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Running Xen

samzenpus posted more than 6 years ago | from the read-all-about-it dept.

Book Reviews 98

David Martinjak writes "Running Xen: A Hands-On Guide to the Art of Virtualization was published by Prentice Hall, and authored by Jeanna N. Matthews, Eli M. Dow, Todd Deshane, Wenjin Hu, Jeremy Bongio, Patrick F. Wilbur, and Brendan Johnson. The book, which will be referred to as simply Running Xen, was a great resource on Xen and virtualization from the administration side. A wide range of topics was covered from installing Xen all the way up to managing virtual resources, including migrating guest environments. Overall, the explanations were concise and understandable; while the information was presented in a straightforward manner. Running Xen was definitely a useful resource for administering systems with Xen." Keep reading for the rest of David's review.The flow of the book was intuitive, and reasonable; this was especially valuable for discussing a newer technology where the terms could be confusing. Fortunately, the authors kept the language clear so that the reader easily could understand the subject of discussion. This unambiguous presentation of content was a welcomed feature.

Running Xen started with a thorough-enough explanation of virtualization. Several different approaches to virtualization were compared and contrasted, which should help the reader to understand where Xen resides in the whole domain. This first chapter was a great introduction as it provided just the right amount of information. At no point did I consider the explanations to be short or lacking; nor did I feel overloaded with details. The authors seemed adequately aware that the title of the book was Running Xen, and they stuck to that scope.

After the introduction, the book moved right into actually running Xen. This helped to keep the my attention on the subject, and tied back in to the proper flow of the material. At first, the chapter began with baby steps. It introduced the Xen LiveCD, and information on working within the Xen environment. Subsequent chapters moved into a more intermediate level of usage: installing Xen in a third-party distrobution, and running pre-built guest images. Popular third-party distrobutions such as Ubuntu, Gentoo, CentOS, and OpenSUSE were covered; and this section also included instructions for using compiled Xen binaries and building your own from source.

One of the topics I was most interested in was building a custom, minimal guest environment from a particular distro. Chapter 7, "Populating Guest Images", provided all of the information I was looking for along with some other interesting facts. The popular distros were covered again (Ubuntu, Gentoo, etc.), but this time a twist was added to the mix. "Populating Guest Images" started off with installing Windows XP in Xen. This was a complete surprise to me. If you prefer GNU/Linux on the server, but Windows XP on the desktop, and have been looking to consolidate with virtualization; this chapter is a must-read. The chapter also helped solidify the understanding of concepts presented earlier in the book. For example, the first chapter discussed two different types of guests: paravirtual (PV) and Hardware Virtual Machine (HVM). In "Populating Guest Images", the authors led the reader through building guests of each type. The process was presented in a logical fashion which was easy to follow, making the book that much more enjoyable.

Running Xen then moved on to putting the guests on the network. Chapter 10, "Network Configuration", covered several options for networking guest environments in Xen. It would be an understatement to say that this chapter was thorough. Overall, the authors did a great job explaining the differences between the networking options, and how to implement each one. Unfortunately the needs of the reader are variable, so this chapter overflowed with information. The upside was that readers with complex virtualized network segments will not be disappointed. The downside was that I, personally, only really needed a small percentage of the chapter's content. Therefore, much of the chapter was technically irrelevant to me individually.

There was one other unfortunate issue, which occurred in the next chapter. Chapter 11, "Securing a Xen System", contained syntax errors for iptables rules. Mainly one dash was used instead of two when specifying the destination port in some rules. For example, LISTING 11.10 displayed the syntax -dport which caused an error. However, the syntax was correct at other places in the book (LISTING 10.24, for example). Additionally, there was a problem on output formatting where the command prompt and output lines ran together in the print (LISTING 11.11). This could cause confusion for some readers intently following the text.

My only complaint with the book was that the chapter on network configuration seemed to be rather long. For a person working with Xen at a business level, especially mid-size to enterprise, this chapter provided an excellent amount of insight and information. But for the person at home building his/her own test server for simple purposes, much of the content in this chapter was overkill. Additionally the few syntax errors were eye-sores, but any person with iptables experience could easily identify and fix the problems. It is just in my opinion, a published book should be syntactically correct so that the reader is not presented with contradicting results; nor should the reader have to conduct additional searches to rectify mistakes from the book's pages. However, these items are minor and pale in comparison to the outstanding wealth of knowledge in the text.

This book is highly recommended for anyone interested in virtualization with Xen. In addition to the regular paperback, Running Xen is also available on Safari. The paperback additionally includes a coupon code for a 45-day pass to access the book via Safari online.

David Martinjak is a programmer, GNU/Linux addict, and the director of 2600 in Cincinnati, Ohio. He can be reached at david.martinjak@gmail.com.

You can purchase Running Xen: A Hands-On Guide to the Art of Virtualization from amazon.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

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suppositories (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#23714151)

they melt in your ass, not in your hands

Black Mesa played around with Xen for a while... (4, Funny)

Anonymous Coward | more than 6 years ago | (#23714179)

... I don't think the results were favorable.

Re:Black Mesa played around with Xen for a while.. (1)

MR.Mic (937158) | more than 6 years ago | (#23720219)

Resonance Cascade - What happens when you run Windows inside of Windows.

Another near-useless book review. (5, Insightful)

XorNand (517466) | more than 6 years ago | (#23714197)

I don't know why I keeping reading /. book reviews; I never feel like I get much information in exchange for my two minutes. Who is the target audience of this book? What kind of Xen experience did the reviewer have prior to picking up this book? What did he actually learn when he was finished with it? There's too much verbiage attributed to how he "felt" about the book or the style it was written in and not enough hard information.

In my personal experience, Xen isn't that hard to get working. I think I read a single HOWTO and was up and running in an afternoon. I subscribe to the mailing list which is a great resource for the more arcane problems (passing a PCI telephony card to an Asterisk domU, for instance). The developers and veterans are very patient and quite helpful. I was hoping this review would tell me why I should or should not spend money on another Xen resource. Since I feel like I still don't know anything about the book, it has failed to do so.

Re:Another near-useless book review. (0)

shellster_dude (1261444) | more than 6 years ago | (#23714417)

I got into xen when it first became available publicly. Back then, it was a @#$*&@#$! to set up. Since then it has become remarkably easy. In spite of that, I have long wished that someone would invest the time to write a good book on the topic. I am glad to hear that someone finally has. As I recall the worst part was setting up networking, so I can understand why the book would talk about the particular area in great detail. TO XorNand, STFU or don't read the reviews. Obviously the books target audience is people who are interested in setting up Xen, how much more specific do you need to be?

Re:Another near-useless book review. (1, Insightful)

street struttin' (1249972) | more than 6 years ago | (#23714559)

Not only that, but you'd think the slashdot comments would refer to the book, which is the topic of the post, but instead you get comments regarding the technical subject of the book.

Rarely would you ever read a counter point to the reviewer such as, "In my opinion, the book offered X..."

Re:Another near-useless book review. (4, Funny)

bsDaemon (87307) | more than 6 years ago | (#23715365)

Reading articles is too much for most people around here, you think they're going to read a whole book? * end sarcasm *

Re:Another near-useless book review. (5, Funny)

Lord Apathy (584315) | more than 6 years ago | (#23714569)

Does it tell me how to fix my fucking motorcycle?

Re:Another near-useless book review. (-1, Offtopic)

Lord Apathy (584315) | more than 6 years ago | (#23714827)

Dumb ass moderator has no fucking clue what I'm talking about do you? If you did you would be laughing your ass off.

Re:Another near-useless book review. (1)

NotBornYesterday (1093817) | more than 6 years ago | (#23723127)

FWIW, I'm laughing my ass off. Of course, on the down side, I have no mod points to give you.

Re:Another near-useless book review. (1)

Lord Apathy (584315) | more than 6 years ago | (#23723235)

I have reached +5, Funny. I'm happy now.

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23714841)

Parent is not a troll. Nobody's heard of "Zen and the Art of Motorcycle Repair"?

Nope. No one has heard of that book. (3, Informative)

spun (1352) | more than 6 years ago | (#23715157)

On the other hand, most of us have read Zen and the Art of Motorcycle Maintenance. Which still doesn't tell you how to fix your motorcycle, that's what's so Zen about it.

"What's the sound of one hand adjusting a timing belt?"

Re:Nope. No one has heard of that book. (1)

Lord Apathy (584315) | more than 6 years ago | (#23715373)

And that would be why I think my comment was so funny. Just like your timing belt comment. Now that is humor.

Re:Nope. No one has heard of that book. (2, Funny)

spun (1352) | more than 6 years ago | (#23715415)

Oh yes, I got that. Poor, sad little humor impaired moderators.

Re:Nope. No one has heard of that book. (1)

Lord Apathy (584315) | more than 6 years ago | (#23715681)

I'm not sure but I think I've just been zinged.

Re:Nope. No one has heard of that book. (1)

spun (1352) | more than 6 years ago | (#23715735)

No, no. Seriously, the moderators are the ones who needed zinging.

Re:Nope. No one has heard of that book. (1)

qnetter (312322) | more than 6 years ago | (#23715645)

Not especially unexpected, considering Ian Pratt et al's original paper was Xen and the Art of Virtualization...

Re:Nope. No one has heard of that book. (1)

ianare (1132971) | more than 6 years ago | (#23715763)

"What's the sound of one hand adjusting a timing belt?"
Your question can be best answered by another question -- "what is the sound of one piston clapping?"

Robert Pirsig has a DVD out (1)

MichaelCrawford (610140) | more than 6 years ago | (#23716541)

You can purchase it through a devoted fan's website [robertpirsig.org] . The site also has the guy's PhD thesis on The Metaphysics of Quality.

ZATAOMM made a huge difference to my life when I first read it, so I was very eager to read Pirsig's second book, Lila, but I just couldn't get into it.

I've been meaning to try again though because Pirsig says the discussion of philosophy is much deeper in Lila.

Re:Robert Pirsig has a DVD out (1)

spun (1352) | more than 6 years ago | (#23716839)

Lila was gilding the lily, as far as I am concerned. He arrived at a very deep and simple conclusion in ZATOMM. In Lila he attempts to gussy up that conclusion with all sorts of derived details. Interesting, but not as profound as his first book.

Re:Nope. No one has heard of that book. (0)

Anonymous Coward | more than 6 years ago | (#23718399)

"What's the sound of one hand adjusting a timing belt?"

I can tell you from experience that, one hand or two, it is a continuing loud metallic banging accentuated by a steady stream of quite inventive profanity!

Re:Another near-useless book review. (1)

A nonymous Coward (7548) | more than 6 years ago | (#23715699)

Here's a hint for dumb-ass moderators on crack: This book should have been called Zen and the Art of Xen.

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23716031)


Does it tell me how to fix my fucking motorcycle?

Hmmm I don't know if you would really want to fix a motorcycle that could fuck. People would pay to see that.

Re:Another near-useless book review. (3, Funny)

Fastball (91927) | more than 6 years ago | (#23716171)


Does it tell me how to fix my fucking motorcycle?

Xen's dead, baby. Xen's dead.

Re:Another near-useless book review. (1)

gzerphey (1006177) | more than 6 years ago | (#23716311)

Netcraft confirmed it.

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23718199)

Does it tell me how to fix my fucking motorcycle?

Xen's dead, baby. Xen's dead.


Now *this* is truly worthy of a +1, funny

Re:Another near-useless book review. (1)

kiehlster (844523) | more than 6 years ago | (#23714673)

At least it wasn't a blatant /vertisement, but I have to agree, this was useless and maybe obvious. My impression makes me believe this is no more than a rehash of the installation guide and some first-hand suggestion. It sort of rings, "If you need the install guide written in easier to follow English, this guide is highly recommended."

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23715077)

Who cares? Xen sucks anyway. KVM is much better...

Re:Another near-useless book review. (1)

bwhaley (410361) | more than 6 years ago | (#23715201)

I don't know why I keeping [sic] reading /. comments. I never feel like I get much information for my 30 seconds. What is this uber-useful xen mailing list? There's too much whining about how people "feel" about the article but no meat.

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23715401)

I don't know why I keeping reading /. book reviews; I never feel like I get much information in exchange for my two minutes.

Two minutes? That is way too much time. You need to learn the Slashdot Book Rating System.

If the rating is greater than 9, run out and buy the book.
If the rating is equal to 9, only read the book if you are particularly interested in the subject.
If the rating is less than 9, avoid the book like the plague.

Re:Another near-useless book review. (1)

sirius-one (1304769) | more than 6 years ago | (#23716745)

Actually, the information about the networking chapter made me much more interested in getting and reading this book. The reviewer may not have cared much, nor does XorNand, but the second time I set up Xen was a server for a startup, and I really needed more information in a hurry about networking. Hope the rest of the book is as detailed...

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23720463)

passing a PCI telephony card to an Asterisk domU, for instance
*Shudder* Is there a good reason, besides "you can"?

At some point (way before this), you have to draw the line and say this machine/service should not be consolidated...

I used to like Linux a lot more before people started bringing it (and affiliated software) in with this "because I can" attitude to work.

I swear to God, if my shop migrates from SPARC Solaris, Clariions & Fibre channel to Xen, iSCSI, & CentOS I will fucking kill somebody.

Re:Another near-useless book review. (1)

stry_cat (558859) | more than 6 years ago | (#23723853)

I don't know why I keeping reading /. book reviews; I never feel like I get much information in exchange for my two minutes.
I must agree on this. While certainly any review should tell us how the reviewer "felt" about the book, there needs to be some hard facts too.

In my personal experience, Xen isn't that hard to get working. I think I read a single HOWTO and was up and running in an afternoon.
Very similar to my experience. The HowTo over as xensource was quite adequate.

I subscribe to the mailing list which is a great resource for the more arcane problems (passing a PCI telephony card to an Asterisk domU, for instance). The developers and veterans are very patient and quite helpful.
Now here is where I disagree. Most of my questions go unanswered or if I do get a reply it is more like the blind leading the blind. What I've read on the list indicates that the folks are more friendly and helpful than the typical opensource list. So I suspect my questions are just getting lost in the huge volumne of the list or maybe I'm just doing stuff that is more arcane than most people. Regardless, the mailing list has been almost useless for me and I'm desperately seeing another resorce.

I was hoping this review would tell me why I should or should not spend money on another Xen resource. Since I feel like I still don't know anything about the book, it has failed to do so.
Yep I agree. The review left a lot to be desired. I hope my local BN or Borders will have it on the shelf so I can skim it before buying it.

Re:Another near-useless book review. (0)

Anonymous Coward | more than 6 years ago | (#23736677)

The reviews are mostly an exercise in self-promotion:

David Martinjak is a programmer, GNU/Linux addict, and the director of 2600 in Cincinnati, Ohio. He can be reached at david.martinjak@gmail.com.
There is occasionally utility to the comments though, especially when the authors get involved. Usually at some point someone seems to come along and offer real criticism of the book. Skip the review and read the comments.

Hardware & Appliance Guide? (0)

Anonymous Coward | more than 6 years ago | (#23714299)

Was there any mention in the book of Xen hardware, pitfalls, recommendations, and so on? I am trying to evaluate a number of hardware appliances like this one from 360is [360is.com] (PDF) and ahead of projects like the SPEC benchmark there is a lack of information.

AG.

Does XEN have a future? (5, Interesting)

Anonymous Coward | more than 6 years ago | (#23714467)

Haven't the kernel developers basically given xen the cold shoulder, preferring now to dedicate their efforts to kvm, the virtualization solution which is now part of the mainline kernel? The problem, from what I recall from reading some threads on the subject a while back was that xen needs to keep pace w/ kernel driver development work, which is an extra effort for the developers. It's easier for them with kvm since it's part of their dev tree. Right now I think Ubuntu is the only big distributer shipping kvm; Redhat et al are doing xen .. I think (corrections please). On that count, xen is doing well. But moving forward, it seems like they have to do a lot of extra work to track kernel development, which will be made harder by virtue of the fact that key kernel developers may not feel like devoting time to what they feel is a duplicate effort.

Re:Does XEN have a future? (-1)

Anonymous Coward | more than 6 years ago | (#23714935)

Xen pretty much just sucks. KVM is a bit (but not much) better. Really the only thing that works right now is VMware ESX....

Re:Does XEN have a future? (1)

Doug Neal (195160) | more than 6 years ago | (#23716105)

Xen pretty much just sucks. KVM is a bit (but not much) better. Really the only thing that works right now is VMware ESX....
Xen's hypervisor and paravirtualisation technology are sound. The thing that lets it down is the infuriatingly temperamental pile of shell scripts that hold it all together. In my experience, if you don't get everything "just so", be prepared for a lot of cryptic and misleading error messages and verbose but unhelpful log files.

Re:Does XEN have a future? (1)

element-o.p. (939033) | more than 6 years ago | (#23716159)

Xen pretty much just sucks. KVM is a bit (but not much) better.

Because?

I've only got a (very) little experience with Xen, but in my brief introduction, it seemed to work pretty well. If there's something about Xen that doesn't work/doesn't work well I'd be really curious to learn what it is before I try to implement it somewhere.

As it is, it just sounds like you are slamming Xen and KVM because you happen to like VMWare (which in my opinion is a PITA, because I couldn't consistently get VMWare to run with the client binary unless I reran the setup script and restarted the daemon(?) process in /etc/init.d on my Gentoo desktop until I wrote a script to handle all of that for me...and it still occasionally pukes).

Re:Does XEN have a future? (4, Informative)

squiggleslash (241428) | more than 6 years ago | (#23715359)

Xen and KVM are completely different types of virtualization solution. The supposed rivalry between the two is largely bad journalism, not rooted in anything to do with the platforms themselves.

If you want to run a single physical computer with multiple operating system instances, such as replacing a bank of servers with a single machine, Xen is your guy. If you want to run VMs under Linux, KVM is your friend. Conflating the two is like comparing... well, to use a car analogy, for this is Slashdot, a railroad with a tractor trailer.

Expand on that please.. (1)

refactored (260886) | more than 6 years ago | (#23715613)

Car analogies are all well and good.... but can we have some detail on that.

And where does virtualbox fit in with all this?

Re:Expand on that please.. (1)

squiggleslash (241428) | more than 6 years ago | (#23724733)

I can't expand on it here because Pudge thinks that 4k is a really big message, and I really can't be bothered any more to navigate through the unholy fuck-up that is Slashcode today.

However, I did write something on Multiply that essentially explains the whole issue. [multiply.com] If you understand why KVM and Xen are entirely different explanations, you understand why a desktop system like Ubuntu was never going to "choose" Xen as a "virtualization solution", and probably shouldn't have even considered it back when they were. Likewise, the only reason a sysadmin would run KVM (or its predecessors such as VMWare) to replace a host of server machines is either out of desperation because a specific Xen issue, or out of ignorance. Xen has no competitors (thus far), but it has a narrow focus of application, and much of the bad-mouthing it gets is because of people who use it when something like KVM or VMWare would be much more suitable.

Thanks, that was interesting... (1)

refactored (260886) | more than 6 years ago | (#23741599)

I'm actively researching the whole area with a view to rolling the "run a windows app on an ubuntu desktop" scenario out to a collection of colleagues.

An interesting counterpoint to what you're saying is coming from Ulrich Drepper [livejournal.com] the libc guy.

Re:Thanks, that was interesting... (2, Informative)

squiggleslash (241428) | more than 6 years ago | (#23747531)

Counterpoint? Drepper's not explaining that the "KVM and Xen are competitors" war is valid, he's just buying into it without justifying it. He doesn't "get" Xen so he assumes it's used in the same areas as KVM and that, therefore, crude performance comparisons are valid. I've not really read much of his stuff before, so it'd be inaccurate to say I've lost respect for the guy on reading that article, but it does sound like he's "not getting it" which reflects somewhat poorly on him. I know I made the right decision putting Xen on my firewall/gateway server, I can't imagine even considering virtualization for a network-accessable no-monitor/keyboard box sitting in my closet. I also know that I wouldn't want Xen on my desktop.

Saying "These both do virtualization therefore one is better than the other" is as silly as saying "Bluetooth and Wifi are both "doing wireless" therefore one is better than the other." The only way to make KVM usable in the area Xen excels is to refactor it so that Linux runs underneath it, not over it. This, of course, means it'll not be KVM, and it'll become a less than ideal application for desktop virtualization.

Likewise Xen can be refactored so it runs under Linux rather than vice-versa. Then it'll be hampered by Linux's limitations, and for the most part by GNU's too. There's no good reason to do this, there already are numerous desktop virtualization systems out there, why undermine the only viable server virtualization system in an effort to compete in an area that already has numerous alternatives?

If you want to compare KVM's performance, do it against its actual rivals like BOCHS and VMWare. If you want to compare Xen's... well, right now you have nothing to compare it to. You have to either say it's good enough for you, or it isn't, and if it isn't, buy multiple machines. If Drepper and others want to produce an alternative to Xen, they need to first understand what it is, why it's useful, and what it's used for. Clearly, if they're going to assume KVM is an alternative, they haven't bothered.

Hmm. I'm still not getting it! (1)

refactored (260886) | more than 6 years ago | (#23755559)

Sorry to so try your patience.... but I've reread your multiply.com article _and_ Dreppers two and I'm still grasping for a good statement along the lines...

When I want to do XXX then Xen is better than Kvm because this aspect of XXX demands YYY which Xen not Kvm provides.

Currently I'm guessing XXX is "I am an Colocation / ISP and want run a bunch of OS instances so that it effectively appears to my customers that they are the only one using this server, but actually are sharing the cost of the hardware with several others."

What I'm missing is what the YYY is that Xen provides but Kvm does not, or Kvm does so too poorly.

As far as I understand Xen requires a priviledged Dom 0 OS, (which you can't on sell to your customers), with Kvm that priviledged OS is Linux.

Is the use case then, "I am colocation ISP and for some reason I must use something other than Linux as the priviledged Dom 0 OS, and I want to run a bunch...."?

Sorry for my obtuseness.

I get the blue tooth vs Wifi analogy. Blue tooth must be wearable and off the power grid hence sacrifices speed and range for lightness and battery life. Wifi is aimed at wired in base stations serving "luggable" laptop size clients that are probably going to be plugged into a power socket, serving "a business" size area at high speed.

What I'm grasping for is a similar clear statement of fit for Xen and Kvm and the reasons.

Re:Does XEN have a future? (2, Informative)

segedunum (883035) | more than 6 years ago | (#23716697)

Xen and KVM are completely different types of virtualization solution.
Well yes they do do things differently, but KVM does it better and simpler by just running on Linux as the base system hypervisor. From a maintenance point of view things get far simpler, as the OP said.

If you want to run a single physical computer with multiple operating system instances, such as replacing a bank of servers with a single machine, Xen is your guy. If you want to run VMs under Linux, KVM is your friend.
That statement is just, well, daft. You're implying that Xen can't run VMs under Linux but KVM can, or Xen can run VMs on systems other than Linux or something that KVM can't do? They're both Linux only at this point, and Xen effectively runs a forked version of Linux because it isn't, and won't be, upstream.

Re:Does XEN have a future? (0)

Anonymous Coward | more than 6 years ago | (#23718125)


That statement is just, well, daft. You're implying that Xen can't run VMs under Linux but KVM can, or Xen can run VMs on systems other than Linux or something that KVM can't do? They're both Linux only at this point, and Xen effectively runs a forked version of Linux because it isn't, and won't be, upstream.

Errr.... Wasn't Xen developed on NetBSD?

Re:Does XEN have a future? (1)

netcrusher88 (743318) | more than 6 years ago | (#23721839)

I think the difference GP is trying to point out is that Xen is targeted more for the VMWare ESX market - the dom0 OS can (and should) be as stripped down as possible - whereas KVM is (currently) more targeted for the VMWare Workstation or QEMU market of bolting a VM onto an existing general-purpose system. That could change on both counts, and kvm developers have stated that they intend it to be general purpose, so there's really no reason that Xen could not be ported to kvm, as it were.

Re:Does XEN have a future? (1)

jdowland (764773) | more than 6 years ago | (#23723591)

The vmware esx bare-bones OS is as Linux derivative. So it's more like KVM in that regard than Xen.

Afaik, the *real* difference is KVM does no paravirtualisation, it is purely a kernel interface to the VT extensions on newer x86 chips. So it's "cleaner", but is no use if you don't have the VT extensions.

Re:Does XEN have a future? (3, Informative)

TheRaven64 (641858) | more than 6 years ago | (#23724191)

You're implying that Xen can't run VMs under Linux but KVM can, or Xen can run VMs on systems other than Linux or something that KVM can't do? They're both Linux only at this point, and Xen effectively runs a forked version of Linux because it isn't, and won't be, upstream.
Xen is a hypervisor. It runs under Linux, not on top (although the Xen devs do often run Xen in KVM for development). It uses one or more slightly (or very, depending on your hardware) privileged guests to provide drivers. These can be Linux, NetBSD or Solaris.

KVM only works on systems that support hardware virtualisation. Xen will run unmodified operating systems on these platforms, but also supports paravirtualised guests on older systems (and paravirtualised guests are faster on any hardware). As far as I know, KVM is x86-only, while Xen runs on x86, PowerPC, Itanium and ARM (Samsung are doing some very cool things with Xen on ARM).

There are a few things that Xen supports that KVM doesn't, such as live migration. This is probably the right time for the obligatory plug for my book [amazon.co.uk] , if you want to learn more about how Xen works.

Re:Does XEN have a future? (2, Informative)

David Jao (2759) | more than 6 years ago | (#23729519)

There are a few things that Xen supports that KVM doesn't, such as live migration.

Wait, what? KVM supports live migration [qumranet.com] , and in fact KVM supports it better than Xen ever did.

Xen allows live migration only between machines with identical or very similar processors. KVM supports live migration between any two systems that can run KVM. For example, if you want to live migrate from an Intel to an AMD host, KVM is your only option. If you want to live migrate a 32-bit guest between a 32-bit host and a 64-bit host, KVM will do that, Xen won't.

Re:Does XEN have a future? (1)

segedunum (883035) | more than 6 years ago | (#23786551)

Xen is a hypervisor. It runs under Linux, not on top
Yes, I know. That's the maintenance problem the OP is pointing out, and its future development doesn't look as great as KVM's does outside of the kernel.

Re:Does XEN have a future? (1)

TheRaven64 (641858) | more than 6 years ago | (#23790507)

Linux is completely irrelevant to Xen. Xen runs quite happily with a NetBSD or Solaris domain 0. It has no dependency on Linux. In a particular configuration, it might have a dependency on a driver only available for Linux, but that is all.

Re:Does XEN have a future? (1)

segedunum (883035) | more than 6 years ago | (#23825603)

Linux is completely irrelevant to Xen.
It requires a patched Linux, or another OS, to provide its device support, which is completely pointless. Same difference.

Re:Does XEN have a future? (3, Informative)

squiggleslash (241428) | more than 6 years ago | (#23725055)

Well yes they do do things differently, but KVM does it better and simpler by just running on Linux as the base system hypervisor. From a maintenance point of view things get far simpler, as the OP said.

Sure, and Wifi does it better and simpler than Bluetooth by using Ethernet frames (The Bluetooth vs Wifi "war" is also a good example of where geeks get it completely, 100%, wrong by not recognizing the entirely different applications the technologies are aimed at.) You're comparing apples to oranges, and assuming that because KVM works better in a specific scenario that it works better.

That statement is just, well, daft. You're implying that Xen can't run VMs under Linux but KVM can, or Xen can run VMs on systems other than Linux or something that KVM can't do? They're both Linux only at this point, and Xen effectively runs a forked version of Linux because it isn't, and won't be, upstream

It's not daft, your response makes no sense. Let's break it down:

You're implying that Xen can't run VMs under Linux but KVM can

That's right. Xen cannot run VMs under Linux. Xen runs VMs on the bare hardware. In the Xen environment, operating systems run under Xen, not vice versa. The only way to run Xen "under" Linux is to run it in an emulator!

or Xen can run VMs on systems other than Linux or something that KVM can't do?

This sentence makes no sense as is. It can't run VMs under Linux, as stated above. In terms of operating system support, you can run various operating systems under Xen as "dom0". Dom0 is a special domain that most hardware is managed by by default (though you can redirect any almost piece of hardware to be managed by any guest system. For example, on my home server, one of the Ethernet cards is managed completely by a domU.) Dom0 can be one of many operating systems, including Linux-based systems, OpenSolaris/SunOS, OpenBSD, NetBSD, and certain versions of FreeBSD (with certain versions of Xen.) The only restrictions that go with being dom0 have to do with the kernels for those systems being Xen-aware.

This flexibility brings enormous advantages incidentally. With enough memory, you can install something like Solaris as your domU and have it export NFS shares upon a ZFS file system to all of the domUs, giving every operating system you run the advantages of the host. At the other extreme, you can install something small and light - bugs aside, I found Xen's integration with Ubuntu Server 8.04 LTS wonderful when setting up my little firewall-gateway/servers box. I have the barest Ubuntu Server installation (no X11/GNOME/etc) as dom0, and even barer systems for the domUs It's great.

They're both Linux only at this point, and Xen effectively runs a forked version of Linux because it isn't, and won't be, upstream.

Xen is PowerPC, ix86, and AMD64 at the moment. In terms of operating systems it can run as dom0, see above. In terms of operating systems it can run as domU, well, the choice is massive.

Really, what you're saying convinces me you haven't really investigated what makes Xen Xen. I would never install Xen on my laptop. I'd never install KVM on my server machine. Take another look at both, and see why their strengths make them suitable for different purposes, neither are solutions that fit every application, and they complement each other well in terms of the applications they efficiently support.

Re:Does XEN have a future? (1)

segedunum (883035) | more than 6 years ago | (#23786679)

You're comparing apples to oranges, and assuming that because KVM works better in a specific scenario that it works better.
Hmmmmm, no. They're both virtualisation technologies, and the point is KVM's future looks a hell of a lot better as part of the kernel than Xen's outside of it. Nice try though.

Xen runs VMs on the bare hardware. In the Xen environment, operating systems run under Xen, not vice versa. The only way to run Xen "under" Linux is to run it in an emulator!
Yep. There's the problem being described ;-). It's a daft way to do things when you can just use Linux itself as the hypervisor, and what you've described there is a pointless waste of time.

Really, what you're saying convinces me you haven't really investigated what makes Xen Xen. I would never install Xen on my laptop. I'd never install KVM on my server machine.
That makes no sense at all because there's no dividing line between the two that you've described. Calling them different does not make them so. Xen's approach is simply daft. They're trying to take the OS and kernel out of the equation by having a bare hypervisor (all that hypervisor is the OS bollocks we've heard), but all they've done is forked the Linux kernel to do so - so yes, they are running it under Linux, just not the Linux.

Re:Does XEN have a future? (1)

Wesley Felter (138342) | more than 6 years ago | (#23715377)

Red Hat is now pushing KVM, see http://ovirt.org/ [ovirt.org]

Re:Does XEN have a future? (1)

Znork (31774) | more than 6 years ago | (#23715643)

As far as I can tell, Redhat is pushing libvirt, which is vm agnostic (you're supposed to be able to use it to manage whatever virtualization tech you want to use).

KVM is nice and shows promise, but performance wise the paravirtualized approach of xen is still significantly faster (as in very-near-bare-metal, even significantly faster than vmware ESX on most loads).

Re:Does XEN have a future? (1)

Quikah (14419) | more than 6 years ago | (#23715839)

What loads are these that Xen is significantly faster than ESX? All of my testing has seen same or slower performance.

Re:Does XEN have a future? (1)

Rob_Bryerton (606093) | more than 6 years ago | (#23716455)

On CPU bound workloads, especially any CPU bound task that is "SMP aware", Xen leaves ESX in the dust, especially when using 2, 3 or 4 virtual CPUs. I'm not talking percentage points here, I'm talking Xen simply *smokes* ESX. I run both Xen and ESX at work on current enterprise grade hardware, and for Linux hosts at least, there's just no comparison.

My experience with ESX is that adding virtual CPUs buys you very little (it's almost a complete waste), whereas with Xen, the performance scales nearly perfectly with each CPU that is added, provided the software is written to efficiently utilize SMP.

On the management front, nothing touches Virtual Center, not even close...

Re:Does XEN have a future? (1)

Quikah (14419) | more than 6 years ago | (#23716675)

CPU bound workloads such as? I have never experienced anything like you described.

Re:Does XEN have a future? (1)

swb (14022) | more than 6 years ago | (#23717205)

In ESX class, we were told (and this is a gross paraphrasing from something the instructor mentioned off the cuff 6 months ago) that multiple virtual CPUs helps most with VMs that run a lot of monolithic processes, as the ESX CPU scheduler is biased towards running on whatever CPU is available, which apparently can hammer cache coherency for SMP-aware multithreading. I think he said that setting processor affinities helps, but can hurt in other ways as well as being incompatible with VMotion.

I think that at the end of the day, though, stuff like VirtualCenter/VMotion/HA kind of matters more than simple CPU performance. Usually its SAN I/O that starts suck giant donkey dorks under VMWare, long before anyone complains about CPU.

Re:Does XEN have a future? (1)

loki-yo (730813) | more than 6 years ago | (#23717669)

On CPU bound workloads, especially any CPU bound task that is "SMP aware"

The immense majority of real life task are not CPU bound anymore with current multi-core CPUS, but RAM and IO bound.

Re:Does XEN have a future? (1)

Znork (31774) | more than 6 years ago | (#23729581)

On the management front, nothing touches Virtual Center, not even close...

Unless you're using Linux desktops. I've seen rumors about the VIC client coming to linux, but after, what, three, four years of customers asking for it? From the point of view of virtualizing linux, the lack of interest in supporting Linux has pretty much negated the advantages of virtual center.

In the long run, a lot of what virtual center does isn't that hard to replicate with standard linux infrastructure (HA, resource management, provisioning, migration, etc), and the ability to leverage host OS capabilities will only make it easier over time.

Re:Does XEN have a future? (1)

Znork (31774) | more than 6 years ago | (#23728927)

Are you testing paravirtualization or hardware assisted full virtualization? (I'm talking about paravirtualized, the full virtualization would match your experience)

Examples; iterative shell scripts (ie, anything with lots of forks and execs) had a huge difference. IO performance varied, but xen tended to be significantly faster on anything read-related. Kernel compilations on multiple virtual machines, fair amount of difference. CPU bound, slight but measurable difference.

Re:Does XEN have a future? (2, Informative)

Richard W.M. Jones (591125) | more than 6 years ago | (#23715953)

KVM is nice and shows promise, but performance wise the paravirtualized approach of xen is still significantly faster (as in very-near-bare-metal, even significantly faster than vmware ESX on most loads).

VirtIO [lwn.net] , which is in latest versions of KVM, paravirtualizes all the hardware and gives you almost all the benefit.

KVM is where things are going because as a poster said above, it avoids having to write all the drivers twice over [livejournal.com] . Xen dropped the ball by not working closely with the Linux kernel developers. Now XenSource have been bought out by a Microsoft proxy [theregister.co.uk] , so the future for Linux & Xen is looking even less rosy.

As you say, Red Hat offers libvirt [libvirt.org] which hides the differences between virtualization systems, so for most administrators and application programmers, which system "wins" is not going to matter. (My personal opinion is that none of them will win outright, at least not for many many years - different approaches to virtualization are suitable for different areas).

Rich.

Re:Does XEN have a future? (1)

Znork (31774) | more than 6 years ago | (#23730055)

paravirtualizes all the hardware and gives you almost all the benefit.

Have you tested it/what performance levels does it have? It's been a bit too immature to push in the corporate setting yet, but it would be interesting to see if it's getting comparable performance now.

Xen dropped the ball by not working closely with the Linux kernel developers

Oh, I agree, duplicating kernel work in the hypervisor is idiotic and a long term dead end, wether it's vmware or xensource doing it.

so the future for Linux & Xen is looking even less rosy.

Yes, well, it's still GPL. But sure, if it hadn't had Redhat and several other companies working on it, I wouldn't touch it with a ten foot pole after the Citrix purchase.

My personal opinion is that none of them will win outright, at least not for many many years

I agree; as technologies they'll all stay around for a long time or the features and advantages will get merged into something user-configurable. Wether the companies built around them will stay around is another matter; commoditization tends to wreck havoc on some business plans.

Re:Does XEN have a future? (0)

Anonymous Coward | more than 6 years ago | (#23717433)

Do you know that VMware ESX 3.5 also uses paravirtualization when available in the guest os?

Re:Does XEN have a future? (1)

loki-yo (730813) | more than 6 years ago | (#23717589)

Anyone who pretends that Xen is supperior because of paravirtualization doesn't know what he is talking about.
1- VMware has paravirtualization also
2- paravirtualization only helps so much, and only with very recent linux hosts
3- paravirtualization is probably going to be useless (as in, not an improvement) once CPUs with virtualizable MMUs get common (shuch as lasts AMDs).

Re:Does XEN have a future? (1)

pmgst17 (524425) | more than 6 years ago | (#23715891)

Right now I think Ubuntu is the only big distributer shipping kvm; Redhat et al are doing xen .. I think (corrections please).
Fedora 9 has kvm, qemu, and xen.

What's amusing is how David loves on Ubuntu, and fails to mention RHEL / Fedora.
"Popular third-party distrobutions such as Ubuntu, Gentoo, CentOS, and OpenSUSE were covered; "
(OK, so CentOS was mentioned, but not RHEL),

"The popular distros were covered again (Ubuntu, Gentoo, etc.), but this time a twist was added to the mix"

Re:Does XEN have a future? (1)

oopsigotroot (1304745) | more than 6 years ago | (#23716453)

Fedora is indeed discussed in "Running Xen" as well.

Re:Does XEN have a future? (2, Interesting)

jandersen (462034) | more than 6 years ago | (#23720615)

Haven't the kernel developers basically given xen the cold shoulder, ...?
They may have, but I think Xen still has a future - just take a look at Oracle VM. Oracle is a substantial player in the marketplace, whatever else one may think of them, so Xen does have some serious backing. Oracle VM is, as far as I can see, little more than a basic Linux with Xen - "perfect for running Oracle Unbreakable Linux" :-) I've tried it, though, and it works well.

Re:Does XEN have a future? (3, Insightful)

David Jao (2759) | more than 6 years ago | (#23721439)

Xen has pretty much no support for laptops. Unfortunately for Xen, it's becoming pretty clear that laptops are the future as far as general purpose computing goes. So I would say that Xen has no future.

The problem (and it is a showstopper) is that Xen has no ability to perform power management. Even worse, the design of Xen makes it almost impossible to support power management in any sane way. In Xen, every OS on your system runs in a virtual machine. Even the so-called "host" OS, which has special privileges for hardware access, runs in a virtual machine. The actual host kernel is a bare-bones hypervisor with so few features that it cannot be called a full-blown OS.

Power management is very difficult to do under the Xen architecture, because ACPI [wikipedia.org] power management requires all of the power management code to run in the OS. Now, an OS running inside a VM has no ability to monitor power usage for other VMs -- that's the whole point of a VM, after all. So, under the Xen design, the power management code cannot run in the "host" OS. It has to run in the hypervisor.

However, power management is complicated enough, and involves enough dependencies, that by the time your hypervisor has implemented power management, it is already bloated and featureful enough to constitute a full-blown OS. Therein lies the problem: a full-blown OS is very difficult to develop in this day and age, and in order to succeed you need a large team. If you screw up, then the resulting product is fragile and unstable, and nobody wants that. Xen is a very small team compared to Microsoft, or Linux, or even FreeBSD. They have no chance to develop an OS on their own.

One might be tempted to implement some sort of passthrough design where the hypervisor piggybacks off of the power management code in the "host" OS, but such a design requires forking the "host" OS and still involves almost as much hypervisor bloat as implementing power management itself.

In short, KVM is the future, at least for regular users like you and me. KVM has no problems with power management, because under KVM the actual host kernel is the exact same Linux kernel that you normally use, with a complete ACPI implementation. Xen might have a place when it comes to big iron and server rooms, but history shows that very few technologies can survive in server-only space when there is mass-market competition (Itanium anyone?).

In fact, with the soaring cost of energy these days, power consumption is becoming a huge issue even on servers, so it's fair to say that Xen's days are numbered even in the server space unless they drastically change their design.

Re:Does XEN have a future? (1)

squiggleslash (241428) | more than 6 years ago | (#23726461)

Xen has pretty much no support for laptops. Unfortunately for Xen, it's becoming pretty clear that laptops are the future as far as general purpose computing goes. So I would say that Xen has no future

Here's a rewording that I think is more appropriate: Xen has sub-optimal support for laptops. As laptops appear to be the future as far as personal computing goes, Xen has little future in that area.

But it never did. Xen was never the optimal solution for desktops. Desktop users generally have no desire to run more than one operating system on a permanent basis. They want transitory access to virtualization. Only if you believe that the only use for virtualization is to run guest operating systems in the transitory way desktop users desire would you suggest that the future of Xen is dependent upon the success, or lack of it, for laptops.

You're fighting a war that doesn't need to be fought. The two systems, KVM/VMWare/Qeme etc and Xen, are complementary. They are aimed at entirely different applications. Sure, people will try to force fit one solution to the other's area, just as some people think a desktop operating system makes for a good server. But that doesn't mean it's the right approach, or that people will get to a point that the right solution - which right now has momentum and mindshare - is going to disappear.

Xen's days in the server space are dependent upon a superior technology not coming along in the same space. KVM doesn't exist in the same space, it doesn't solve the same problems, any admin who tries to run it there is certainly not doing themselves any favors. And given servers are exactly the kinds of system that are permanently on, running, and sucking up power, it's hard to take seriously the argument that "power management" issues are going to make Xen be seen to be so bad that (rational) admins would seriously consider running everything as VMs on a desktop.

Re:Does XEN have a future? (2, Insightful)

David Jao (2759) | more than 6 years ago | (#23729141)

First of all, I'm not fighting a war here. I'm just saying nature will take its course, and there is nothing you or I can do to stop it.

KVM will scale up to the server space. There is no technical reason why KVM requires "running everything as VMs on a desktop", even though that happens to be required today. In fact I guarantee you that one day KVM will be viable in the server arena. Once that happens, Xen is dead.

By contrast, Xen can never scale down to laptop or even desktop users, because the hypervisor design imposes unacceptable usage constraints for such users.

I said before, and I'll say again, it is very hard for any server-only computing technology to compete against mainstream alternatives. Admittedly, it is easier in the case of software (e.g. Oracle) than hardware (e.g. x86). However, x86 virtualization happens to be moving in the direction of hardware. All of these factors weigh against the hypervisor design. Incidentally, all of Xen's competitors, including VMware and Microsoft, offer at least some virtualization products not based on hypervisors. Xen is the only company tethered to hypervisors, and that does not bode well for them.

You say yourself that "people will try to force fit one solution to the other's area" but then you dismiss this as a non-issue. I think it is a bigger issue than you realize. For example, the reviewer of this book, among all people, complains several times in this review that the book is overkill for what he needs. It looks like he would be better served by KVM. If there is a "war" to be fought, then the goal must be to educate readers about the pros and cons of each option, so that they can choose intelligently. That's all I'm trying to do.

Re:Does XEN have a future? (1)

Bryan Ischo (893) | more than 6 years ago | (#23743027)

But is ACPI support *really* that hard that Xen can't implement it? I don't know the ACPI system at all, but I have to say I doubt it. I would think that managing multiple virtual OS installations is a difficult challenge, and if the Xen team could implement that, would ACPI really present that much of a challenge?

Re:Does XEN have a future? (2, Insightful)

PetoskeyGuy (648788) | more than 6 years ago | (#23731695)

Amazon EC2 is the largest installation of XEN servers I'm aware of. You can sign up right now and start up to 20 virtual machines for $.10 US per hour. There are some major services built on top of EC2. I would assume Amazon itself uses the technology to run their own services - that should provide a pretty good shelf life and development cycle.

Can one migrate a guest from Parallels or QEMU? (1)

MichaelCrawford (610140) | more than 6 years ago | (#23714707)

I run various operating systems under Parallels and QEMU on my OS X MacBook Pro. But I'm looking to build a fairly high-end Linux box that I'd like to run Xen on. Is there a way I could transfer my existing guests to Xen?

No doubt I could figure it out somehow, but a FM to R would sure be nice.

It turns out that you can't boot the BeOS 5 Pro CD under either Parallels or QEMU; the boot loader can't find the kernel, possibly because it accesses the CD drive in a different way than most other operating systems.

I figured out a painful yet effective way to install the BeOS under QEMU: install it on a real machine, then copy its partition into a disk image [oggfrog.com] that's booted under QEMU. It involves a lot of tinkering with dd and sfdisk, a utility that allows one to specify partitions by exact sector numbers.

Re:Can one migrate a guest from Parallels or QEMU? (1)

Znork (31774) | more than 6 years ago | (#23730197)

Easiest way I've seen to do it is to install a -xen kernel in the machine you're about to move, then dd a copy into a file or block device you're planning to use. That works fairly well on fedora/centos paravirtualized hosts on fedora/centos at least.

Another way is to define an external xen-aware vmlinuz and initrd in the vm config file, in which case you should be able to boot pretty much any linux filesystem (provided the initrd does the appropriate things, of course).

Cant say how easy it is with fully virtualized non-linux systems tho, but as Xen HVM assisted vm's use QEMU for most device emulation I suspect you may get similar problems there.

Running... Xen!? (2)

Cctoide (923843) | more than 6 years ago | (#23714783)

If you'll excuse my off-topicness for a moment here, I can't be the only one who was thinking "Wait, someone actually wrote a serious book about Half-Life?" when clicking onto this...

Re:Running... Xen!? (0)

Anonymous Coward | more than 6 years ago | (#23721003)

I think the first clue was the fact that the title is about "running" rather than *cough* "jumping" :)

But yeah, I had the same reaction hehe.

No love for Fedora? (1)

Nushio (951488) | more than 6 years ago | (#23714901)

Seeing how Fedora basically spearheaded development of Xen, including it since Fedora Core 4, I find it hard to believe that there's no mention of it.

Re:No love for Fedora? (0)

Anonymous Coward | more than 6 years ago | (#23715537)

There is definitely coverage of CENTOS which is in essence redhat enterprise linux. Most people doing serious virtualization (those who might be apt to purchase the book) are probably picking enterprise distributions :) Having said that the book does also mention and discuss the redhat virt manager.

No love lost there.. (0)

Anonymous Coward | more than 6 years ago | (#23716163)

Seeing how Fedora basically spearheaded development of Xen, including it since Fedora Core 4, I find it hard to believe that there's no mention of it.
While Fedora use Xen, I think you'll find Citrix, Intel, IBM and HP employ most of the staff who actually contribute to the hypervisor itself. Though I'm sure as an open source project there are many many others.

please provide definition of Xen (1)

SethJohnson (112166) | more than 6 years ago | (#23717675)



In order to increase the relevance of this book review to the slashdot readership, it would be helpful to include in the summary a definition of what Xen (or the book's technological focus) is. I skimmed the book review and still couldn't find a definition of Xen- I wanted to know if it was a free, open source virtual machine emulator. It is [xen.org] . I am not dissing this review. Just trying to provide feedback to this reviewer so the next review can be written to draw more people into reading and learning about the subject of the book.

Seth

Re:please provide definition of Xen (1)

5pp000 (873881) | more than 6 years ago | (#23717789)

What is the sound of the one head seeking?

Xen isn't a silver bullet (2, Informative)

rips123 (654488) | more than 6 years ago | (#23717983)

I've deployed xen at work. It has its issues. A report on these would be much more useful to the slashdot crowd than a book full of information thats largely out of date the moment its published so here goes:

The two biggest issues that bit me:

1. I wanted to use external USB drives in a xen virtual machine. I can do PCI passthrough (exposing a whole PCI device) to a guest but only on linux. Solaris support doesn't exist yet and I think the FreeBSD support is still in the pipeline. Tough luck if you want to run, say, a kernel-based ZFS distro on a guest OS like I did. I ended up using a linux guest with para-virtualized PCI and zfs-fuse but I still have some memory leak issues that mean I have to restart the fuse daemon every so often - not ideal.

2. I wanted to virtualize an old windows PC used to run through web logfiles once a month. Xen can't virtualize DMA access so for hardware virtual machines like Windows XP, you end up with IO based disk access which uses MUCH more CPU than DMA access - especially for this sort of task.

Better than RedHat documentation (2, Informative)

RobNich (85522) | more than 6 years ago | (#23718001)

The book HAS to be better than the documentation that RedHat provides for RHEL 5 Virtualization [redhat.com] . It ranks among the worst-written, most useless documents I've read in a long time.

Re:Better than RedHat documentation (1)

corbettw (214229) | more than 6 years ago | (#23718817)

It ranks among the worst-written, most useless documents I've read in a long time.
You haven't read any of the numerous court orders my ex-wife feels free to continue ignoring.

Re:Better than RedHat documentation (1)

Richard W.M. Jones (591125) | more than 6 years ago | (#23721709)

It's been completely rewritten from scratch for the recently released RHEL 5.2. Not sure why it's not on the site yet, but I imagine it will be soon.

Rich.

Re:Better than RedHat documentation (0)

Anonymous Coward | more than 6 years ago | (#23722447)

The new guide in RHEL 5.2 is completely rewritten and a massive improvement.

Re:Better than RedHat documentation (1)

jdowland (764773) | more than 6 years ago | (#23723605)

I find most RH docs a lot like that unfortunately. I find it quite incredible that it's often easier to find multiple pages explaining how to use the (self explanatory) redhat GUI admin tools but much harder to find documentation for config file syntax and the like.

You only need to know two things about xen: (1)

ack_call (870944) | more than 6 years ago | (#23719059)

xm destroy ./

xm create ./

And hey presto, it's back!

TMI? Seriously? (1)

algae (2196) | more than 6 years ago | (#23719925)

My only complaint with the book was that the chapter on network configuration seemed to be rather long. For a person working with Xen at a business level, especially mid-size to enterprise, this chapter provided an excellent amount of insight and information. But for the person at home building his/her own test server for simple purposes, much of the content in this chapter was overkill.

You know, I can't agree with you there, on account of my being an IT professional evaluating xen for a mid-sized to enterprise business. On one hand, your review told me this book will probably be quite helpful for setting up xen in complex network environments. On the other hand, you seem to be looking for a couple HOW-TO documents and a PHP forum aimed at amateur home installations.

Re: (1)

clint999 (1277046) | more than 6 years ago | (#23726899)

Haven't the kernel developers basically given xen the cold shoulder, preferring now to dedicate their efforts to kvm, the virtualization solution which is now part of the mainline kernel? The problem, from what I recall from reading some threads on the subject a while back was that xen needs to keep pace w/ kernel driver development work, which is an extra effort for the developers. It's easier for them with kvm since it's part of their dev tree. Right now I think Ubuntu is the only big distributer shipping kvm; Redhat et al are doing xen .. I think (corrections please). On that count, xen is doing well. But moving forward, it seems like they have to do a lot of extra work to track kernel development, which will be made harder by virtue of the fact that key kernel developers may not feel like devoting time to what they feel is a duplicate effort.

Is this the book - (1)

Geminii (954348) | more than 6 years ago | (#23749513)

Stashed under the pilot's seat aboard the Liberator?
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