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Basics of RAID

Zonk posted more than 9 years ago | from the brush-up-on-the-essentials dept.

Data Storage 242

Doggie Fizzle writes "RAID has been common in business environments for ages, and is now becoming more viable and popular for personal computers. This article focuses on the the basics of RAID, and spells things out for beginners or tech veterans. From the article: 'The benefits of RAID over a single drive system far outweigh the extra consideration required during installation. Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.'"

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Slashdot: News for N00bs (0, Insightful)

Anonymous Coward | more than 9 years ago | (#13140678)

Anyone ever get the feeling Zonk just doesn't get the Slashdot target demo?

first post and such (-1, Offtopic)

Anonymous Coward | more than 9 years ago | (#13140685)

yay.

Hit 'em when it hurts! (2, Insightful)

Gentlewhisper (759800) | more than 9 years ago | (#13140749)

. Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.

Because otherwise, you can tell them all about the wonders of RAID and all they'll do is just pretend to be interested while secreting thinking that you are some mad geek.

Tell them about the wonders of RAID after they've been kicked in the nuts by a drive failure, and you sure as hell would be getting their whole undivided attention.

Making the most of your effort man.. that's what it is :)

Bah we know this. Teach us how to raid panties! (0)

Anonymous Coward | more than 9 years ago | (#13140688)

We're NERDS. We created raid!

Holy Ads, bat-man! (4, Insightful)

temojen (678985) | more than 9 years ago | (#13140691)

That's an awful lot of ads for a re-hash of well-known info. Are the editors sure this is frontpage worthy? It looks like a blatant attempt to get page views to me.

Re:Holy Ads, bat-man! (1)

trixy_1086 (687653) | more than 9 years ago | (#13140885)

What I find interesting is that a similar reply to yours by an AC got modded as a troll.

Re:Holy Ads, bat-man! (1, Funny)

Anonymous Coward | more than 9 years ago | (#13140899)

You think that's bad. See my article on why SATA is better than IDE. It's only more relevent now than when it was written, 12 years ago.

Re:Holy Ads, bat-man! (4, Informative)

Threni (635302) | more than 9 years ago | (#13140914)

Looks ok to me - not a single one. Want my AdBlock list?

I didn't get any. (2, Informative)

Mustang Matt (133426) | more than 9 years ago | (#13141033)

Adblock must be doing it's job.

Re:Holy Ads, bat-man! (3, Informative)

Nuttles1 (578165) | more than 9 years ago | (#13141048)

Ads...I see them once in a while, but they are quickly added to my adblock list. Really, should tech saavy /. readers see very many ads at all? I think the poster of the parent is a wanna be geek. Ok, enough sluphing off, back to work...

Re:Holy Ads, bat-man! (0)

Anonymous Coward | more than 9 years ago | (#13141050)

Yes, why does every little blog have to have its own advertising campaign to gain income. Is running a website that expensive these days?

raid (4, Funny)

Anonymous Coward | more than 9 years ago | (#13140693)

http://raid.com/ [raid.com]
http://www.killsbugsdead.com/ [killsbugsdead.com]

Re:raid (1)

Pantero Blanco (792776) | more than 9 years ago | (#13140813)

That's made even funnier by the fact that there's a can of it right next to my computer...It protects my data by ensuring that there aren't any roaches to crawl in any open expansion slots and fry my board.

Re:raid (2)

dgatwood (11270) | more than 9 years ago | (#13140994)

Roaches... no, but ants.... Have you ever seen what happens when a few hundred ants crawl inside a computer to get the crumbs that some 133+ computer repair guy dribbled inside it? :-D

http://www.getipm.com/answers/computer-ants.htm [getipm.com]

Raid! (-1, Offtopic)

macdaddy357 (582412) | more than 9 years ago | (#13140697)

Kills bugs dead!

Arbitrary file inclusion! Yay! (-1, Offtopic)

Anonymous Coward | more than 9 years ago | (#13140705)

Fix your scripts, guys:

Warning: main(./files/../Article 7 Page 2): failed to open stream: No such file or directory in /home/btxform/public_html/index.php on line 271

Warning: main(): Failed opening './files/../Article 7 Page 2' for inclusion (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/btxform/public_html/index.php on line 271

Re:Arbitrary file inclusion! Yay! (0)

Anonymous Coward | more than 9 years ago | (#13140880)

I've reported this in their forum. Hopefully somebody will fix it (or at least take the advice under consideration).

Excellent RAID reference (4, Informative)

Logic Bomb (122875) | more than 9 years ago | (#13140706)

There's an excellent guide to RAID levels (with pretty diagrams and such) at http://www.acnc.com/raid.html [acnc.com]

There's a lack of real information about RAID (4, Informative)

mollog (841386) | more than 9 years ago | (#13141081)

I worked for years in development of RAID solutions for a major manufacturer. One of the problems with selling RAID solutions is the lack of understanding, or the prejudice and bias of the people who were supposed to be specifying and buying the hardware.
The 'tutorial' of the parent article is talking in kindergarden terms, oversimplifications and obsolete term, and overlooking some of the issues with using RAID. It's a good example of the true lack of understanding about the subject. By now, there are so many types of solutions that the term RAID hardly applies. But, even 10 years ago companies like Compaq had innovative rudundant storage solutions that were enterprise ready.

Or... (4, Insightful)

Joe5678 (135227) | more than 9 years ago | (#13140714)

A source of information with far better content, that isn't simply an excuse to sell ads.

Wikipedia [wikipedia.org]

Current HDD prices... (3, Interesting)

Manip (656104) | more than 9 years ago | (#13140718)

Depending on the your budget here in the UK you can get an 80Gb HDD for around £35, so split over some time you should be able to afford two (or an extra one if you already have one). This is a good enough reason for anyone to try RAID.

I myself currently have it setup to mirror my data across two 80Gb drives... Four months ago one of the hard disks died (funny buzzing sound, no access) but the manufacturers three year warranty was still valid, so I returned the drive to them for a free replacement. I received the replacement drive and shoved it in, mirrored the data back onto this new second drive and continued as before. If I hadn't have had this setup that data could have been permanently list. It also saves me from writing ten DVDs to store that much.

Re:Current HDD prices... (0)

Anonymous Coward | more than 9 years ago | (#13140747)

The problem is RAID controllers, not drive prices. Most on the market are garbage win-RAID.

Re:Current HDD prices... (5, Insightful)

tool462 (677306) | more than 9 years ago | (#13140792)

You may already know this, but it's worth mentioning to others who read this that may not. Your scheme works great to back up your data in the event of hardware failure, but in the event a virus or errant program corrupts the data, you'll still be wanting the DVD backups. That's because if a virus corrupts some files, it's doing the same thing on both drives, rendering the back up useless. RAID mirroring handles only one very specific type of data security. It's a very useful one, but it's important to understand the limitations or you can get bitten hard.

Alternatively to DVD backups, you can also sync up your data on a regular basis to an external hard drive. This doesn't protect you if your house burns down, like DVD backups kept in a safety deposit box would do, but it does help you restore lost data after it gets corrupted.

Ultimately, all these solutions require varying amounts of money, time, and effort, so you just have to decide what level of security you require and what you are willing to pay for it.

Re:Current HDD prices... (4, Insightful)

ScrewMaster (602015) | more than 9 years ago | (#13140990)

Ultimately, what it comes down to is that mirroring merely makes the hardware more reliable, it is not a backup technique.

Probably better (3, Informative)

abrotman (323016) | more than 9 years ago | (#13140724)

Re:Probably better (1, Informative)

Anonymous Coward | more than 9 years ago | (#13140811)

Arrrggh -- Redundant Array of Inexpensive Disks -- I know that there not necessarily inexpensive now days but that what RAID means -- before you go blabing about how its changed just tell me one thing!.... what the hell would a "dependent disk" be other then one thats already in a RAID???

Re:Probably better (2, Informative)

Joe5678 (135227) | more than 9 years ago | (#13140833)

what the hell would a "dependent disk" be other then one thats already in a RAID???

A dependent disk would be one that can not be swaped out of the configuration. With independent disks you can remove one and replace it with a different one and go on about your way.

Give me RAID 5 (3)

hobotron (891379) | more than 9 years ago | (#13140726)


Seriously, SATA hotswappable RAID 5, put an onboard controller on next gen motherboards, I dont care if its crappy compared to an expansion card, and you will have my money. Yeah we have RAID 0, 1 , 0+1, but no onboard commercial RAID 5 solution in mainstream motherboards. I know its more expenisve, but its also more efficient, and with every failed HD common users encounter the market gets bigger.

Re:Give me RAID 5 (2, Informative)

Ann Elk (668880) | more than 9 years ago | (#13140755)

Slightly OT, but this site [linux.yyz.us] is frequently updated with the current state of SATA/RAID support under Linux.

Re:Give me RAID 5 (3, Informative)

kayak334 (798077) | more than 9 years ago | (#13140854)

I've been using this board [asus.com] from Asus for about 6 months with onboard SATA RAID5. It cost $120 from Newegg.com when I got it, if my memory serves me.

Re:Give me RAID 5 AMEN (0)

Anonymous Coward | more than 9 years ago | (#13140868)

from your mouth to Steve Jobs ears. If anyone will ever make RAID 5 a desktop standard its Apple. Its just too bad the G5 tower only has room for 2 drives. I'd take three 120GB drives in a Raid 5 array over a 300GB drive any day. People need speed and reliability much more than storage these days with the smallest drive you can get most places being 80GB.

Here you go (2, Informative)

kf6auf (719514) | more than 9 years ago | (#13140950)

I am running RAID 5 on my desktop server right here. It has a P4 3 year old Gigabyte motherboard. It's not hotswappable because it's not enterprise level (and I don't plan on having to hotswap all of the time, only when shit happens) but it gives me the RAID 5 that I like to use as a backup using software based RAID on Ubuntu Linux [ubuntulinux.org] . After the install, it it would be just as easy for Grandma to use as if it were not RAIDed and I am certain any /.er could figure out the install for most any Linux distro.

Can I have your money now?

RAID0 (2, Informative)

fredistheking (464407) | more than 9 years ago | (#13140731)

RAID0 will increase your change of failure since you will loose all your data if a single drive fails. RAID0 isn't really redundant.

Re:RAID0 (1)

JonN (895435) | more than 9 years ago | (#13140796)

Yes, it mentions that in the article: RAID 0 is one of the configurations that does not provide redundancy, making it arguably not a true RAID array.

Re:RAID0 (0, Funny)

Anonymous Coward | more than 9 years ago | (#13140809)

Raid0: Kills data dead!

Re:RAID0 (1)

fredistheking (464407) | more than 9 years ago | (#13140881)

I was just pointing it out since the submitter makes it sound like RAID can be equated with redundancy.

Um...Personal Use... (1)

greymond (539980) | more than 9 years ago | (#13140734)

"now becoming more viable and popular for personal computers....Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them"

I was thinking they were referring to "Joe Bob Home User" who is starting to use RAIDS more, which is true but, as far as I have seen they are NOT using it for RAID1 - (Mirroring and Duplexing) they ARE using it for RAID 0 (Striping) so their system apps/games run faster.

Another helpful link (4, Funny)

Toasty16 (586358) | more than 9 years ago | (#13140737)

Here is a link that explains the basics of computer hardware; I think that it's a good companion piece to the RAID article: http://www.angelfire.com/rings/judy_patch/ [angelfire.com]

Re:Another helpful link (1)

Rufus211 (221883) | more than 9 years ago | (#13141045)

The sad part about this link is I can't tell if it's a parody or not. I've heard too many users say similar things.

RAID for "personal computers"? but why? (4, Insightful)

Rosco P. Coltrane (209368) | more than 9 years ago | (#13140739)

Okay I guess it appeals to geeks and fancy computer modders and all. But really, when it comes down to it, a decent main hard-disk, a tray in the second bay for backup hard-disks, and a reasonable backup regimen that people keep up is all a "personal" computer user needs.

Personally, I have 3 backup hard-disks, one that keeps a "clean" base system that I update every 6 months or so, and 2 that I do full differential backups on every 3 days. The "clean" hard-disk is kept off-site, and a script tells me when to do the backups on the other 2. And for very very important files, I just write them on a CD on the spot.

With that, I've yet to lose a single file since I started using Linux in 93 or 94. My solution is cheap and doesn't involve fancy raiding. And I'm quite sure I overdo it, most people could do just fine with one main hard-disk, one backup hard-disk and a little discipline.

Re:RAID for "personal computers"? but why? (1)

DigiShaman (671371) | more than 9 years ago | (#13140783)

I use two SATA drives in RAID-0 for the simple purpose of bandwidth. It's a "must have" when working with 4GB+ AVI and MPG files for Adobe Premiere. Yes, I do video editing for music videos (for friends that need to promote).

Nice theory.... (3, Informative)

dbc (135354) | more than 9 years ago | (#13140850)

... but how often do personal backups actually happen? I'm one of those guys that has been taking home backups seriously for a long time, and has a collection of obsolete tape units to prove it. And backups still do not happen often enough if it requires me handling tape.

Let's face it, discipline is a drag, that is why at work IT people are paid to schlepp around stacks of locked cases full of back up tapes to be shipped off site.

So... for my home file server, I went to RAID mirroring, with a 3rd drive in a drawer. A mount-copy-umount chron job copies to the drawer-drive. Drawer-drive gets swapped and taken off site "when I think of it". Because... RAID only protects you from falling over hard drives. It does not proctect you from:

1) Ooops, I wish I hadn't deleted that.
2) Gack! My house just burned down! And took 10 years of tax data with it!
3) Power supply goes wonky, causing both drives to scribble random scorfulentness everywhere.

A home RAID system does not need to be expensive. Who needs hot swap? Use cheapo PATA drives. A few hours of down time for the wife and kids is OK. It doesn't take a big, bad CPU, and software RAID works great.

Still a single point of failure (5, Interesting)

L-Train8 (70991) | more than 9 years ago | (#13140745)

With RAID, you still have a single point of failure. Instead of it being your hard drive, it is now your RAID controller. So what is the advantage?

Since a RAID controller doesn't have moving parts, is it less likely than a hard drive to fail?

Re:Still a single point of failure (3, Insightful)

Rick Zeman (15628) | more than 9 years ago | (#13140780)

With RAID, you still have a single point of failure. Instead of it being your hard drive, it is now your RAID controller. So what is the advantage?

You get a new one under warranty or buy one...and your data is still there. If your drive dies and you get a new one your data's toast unless you have megabucks for Drive$aver$.

Re:Still a single point of failure (1)

Joe5678 (135227) | more than 9 years ago | (#13140781)

With RAID, you still have a single point of failure. Instead of it being your hard drive, it is now your RAID controller. So what is the advantage?

For a home RAID system, the advantage is you can replace the RAID controller and still have all of your data. Unless of course the RAID controller corrupts all the data, but I'm not sure I've ever seen that happen.

Re:Still a single point of failure (3, Informative)

PhotoBoy (684898) | more than 9 years ago | (#13140847)

I've had my data corrupted by a dodgy controller... twice. I've been having terrible luck with the nvRAID provided on nVidia nForce 4 motherboards. Twice now the machine has locked up and on rebooting the RAID array is reported as damaged and a drive is missing from the array. A bit of Googling has revealed it's a common problem.

Fiddling around in the BIOS disabling and reenabling RAID makes both disks show up again but putting them back into a RAID array seems to do no good as Windows always claims files are missing after doing this. If I reinstall Windows my data is always all still there in perfect condition, the hassle of reinstalling Windows and my apps is a pain though. So it's not totally corrupted, but enough to be a complete bitch.

My feeling on RAID on the desktop is that it's a good idea but at least in nVidia's case it's being done on the cheap and is not totally stable. That said Intel's RAID controllers are superb and I'd use one anyday if it weren't for the vast amounts of heat and inferior performance of the P4.

Re:Still a single point of failure (2, Insightful)

EvilMagnus (32878) | more than 9 years ago | (#13140786)

Yes.

The controller's still a point of failure. Indeed, with some RAID controllers if they go bad they corrupt data on *both* your disks, rendering both unusable.

RAID protects against hardware failure of a drive.
It does not protect against a bad controller or an OS snafu (for example, I once had the MSFT go bad on an NTFS volume, losing all data on a drive. RAID wouldn't have helped me there, either).

So if you really care about your data, you should run RAID in conjunction with an off-disk backup solution. Preferably something that is regularly refreshed and kept seperately from your computer.

Re:Still a single point of failure (-1, Redundant)

Anonymous Coward | more than 9 years ago | (#13140903)

"With RAID, you still have a single point of failure. Instead of it being your hard drive, it is now your RAID controller."

1) If you only have one disk and it fails all your unbacked up data is gone

2) With a mirrored disk if a disk fails your system does not even go down you can take your time replacingthe disk

3) With a mirrored disk if your controller fails you do not loose data

4) Most RAID is done with software so there is no special controller required. A minimum RAID system canbe build with just two IDE drives.

Re:Still a single point of failure (0)

Anonymous Coward | more than 9 years ago | (#13140928)

Yes.

Mechanical devices are always more prone to failure due to regular wear and tear. Where a tape drive might need to be retrofitted every few years, the electrical components behind it often run for years and years.

Besides, even if the RAID controller dies, you do not lose the data. Just go get another RAID controller. The same cannot necessarily be said when the drive head comes smashing down on a platter and leaves a nice gash due to an accidental foot swing.

Re:Still a single point of failure (1)

kosmosik (654958) | more than 9 years ago | (#13140935)

> With RAID, you still have a single point of
> failure. Instead of it being your hard drive,
> it is now your RAID controller. So what is
> the advantage?

What kind of failure you mean? You mean getting your data damaged due to RAID controller failure? I've never heard of something like that but maybe it may happen. But I can bet that it will happen less than harddrive failure - so still having N drives and one controller is less likely to fail than having one hd - means RAID has advantage here...

If you mean aviability - I think this is not the case here. We are talking about data safety. If your RAID controller fails - get a new one, plug it in and it should work. Or maybe get RRAIDC (Redundant Redundant Array Of Inexpensive Discs Controller). But then you will go to other place and find it is single point of failure, than another. :) It is not the case of having single point of failure (you will always find one) - it is the matter of probability of failure.

Now for usual Slashdot bashing - somebody knows how often it is that data is lost (we are talking here about home users) not due hardware failure but software (like you know - Windows bug) one?

> Since a RAID controller doesn't have
> moving parts, is it less likely than a hard
> drive to fail?

Yes.

Re:Still a single point of failure (1)

diegocgteleline.es (653730) | more than 9 years ago | (#13140938)

Instead of it being your hard drive, it is now your RAID controller. So what is the advantage?

Your RAID controller isn't who saves your data, so you don't lose your data, which is the point of several RAID modes?

So use two controllers (1)

Sycraft-fu (314770) | more than 9 years ago | (#13140954)

Our most critical stuff is mirrored on seperate disks that are on seperate backplanes attached to seperate controllers. So the only single point of failure is the system, and if it goes down well the data isn't that useful anyhow.

Also yes, RAID controllers are much less likely to fail. For the most part, if a solid-state device works for the first 30 days, it'll work forever if it's taken care of. There are exceptions, of course, but lacking any moving parts there just aren't a lot of ways for them to wear out, particularly for things that don't generate much heat and thus son't have much thermal expansion/contraction.

With disks it not a question of if, but when they'll fail. Eventually, something will wear out and they'll stop working. Might be 20 years, but it'll happen.

Unfortunately I don't have any empirical data so I'll just relate personal experience, even though it's not a proof: We see probably 10-20 harddrives fail per year for all our systems. Not unreasonable, we have a lot of systems. We see less than 1 harddrive controller fail per year. It almost never happens.

Re:So use two controllers (1)

C32 (612993) | more than 9 years ago | (#13141073)

Ever hear about electron drift?
With todays feature sizes you'll be lucky to get 10 years of 24/7/365 use out of any reasonably complex integrated circuit...

Re:Still a single point of failure (1)

darkmeridian (119044) | more than 9 years ago | (#13141071)

That and when a RAID controller breaks, you can replace it with another one with down time but no data loss. When a hard drive breaks, you can replace it but you lose the data.

Re:Still a single point of failure (2, Informative)

PhunkySchtuff (208108) | more than 9 years ago | (#13141079)

Yes and No.
For a basic RAID, ie a host card in a computer attached to a bunch of disks, then yes, the card is the single point of failure. This is less of a problem than losing a disk because: the card is less likely to fail (as you guessed, no moving parts) and failure of the card doesn't necessarily mean loss of any data. Failure of the RAID card will mean access to the attached RAID array becomes difficult =) however some machines even have hot-swap adapter cards, in which case you swap out the card for a new one and you're back up and running. No downtime, no loss of data.

For the usual kinds of RAID units used in enterprise, they're a hardware RAID enclosure with it's own RAID controller, attached via SCSI or FibreChannel to a host. Some of these units actually have two (or more) RAID controllers in them, each with their own FibreChannel connections (two or more, per controller) and if one controller dies, the other one takes up the slack (with a loss of performance, but not data). Going even further, you can have separate FiberChannel connections from each controller going through separate FC Switches, so even if a FC Switch dies, the SAN doesn't go down...

What's the downside to all this? Big $$$.

Cheers,
Kai

Re:HP 6402 (0)

Anonymous Coward | more than 9 years ago | (#13141088)

My favourite failure was having the array accelerator memory fail (192mb)while I was working on a 2003 server. Unfortunately I was making changes to active directory at the time - and some of the drive writes happened to be in the array memory at the time.....ah bugger....

Money talks (2, Informative)

cazbar (582875) | more than 9 years ago | (#13140751)

Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.

Cuz the boss won't cough up the money until it happens.

Article Summary (0)

Anonymous Coward | more than 9 years ago | (#13140770)

RAID: Redundant Array of Independant (Inexpensive) Disks

Why? If one disk dies you don't lose your data.

RAID 0: better performance, worse reliability
RAID 1: mirroring; no performance benefit
RAID 5: striping w/ parity; perfomance benefit + reliability

How? With Linux of course!!! 50f7w4r3 R41D is teh r0x3r

Really guys, is this article really necessary? There's enough about RAID in basic CompTIA A+. I don't really think this needs to be posted on the front page. But what do I know; I'm just an AC.

Re:Article Summary (0)

Anonymous Coward | more than 9 years ago | (#13141022)

raid 1 gets you a performance benefit while reading. raid 5 has write deficits.

Too expensive (2, Insightful)

pete19 (874979) | more than 9 years ago | (#13140771)

As a (poor) student, I find that I simply can't afford an extra hard drive! I got a 2nd hand DVD burner from a friend for £15 and backup all my really important stuff (Code for university, photos, etc) every week. All my MP3s go on another DVD along with the hard disk, and they're "backed up" on my MP3 player anyway.

As of yet I've never had a single hard disk failure... but I've not really got anything I'm bothered about losing, so RAID isn't worth it for me.

SCSI RAID Yes, IDE RAID No (5, Funny)

Anonymous Coward | more than 9 years ago | (#13140779)

IDE HDD Talking to IDE Controller:
HDD: I'm gonna need more time for that write
Contr: Yeah OK, go ahead good buddy
Contr: What's up?
Contr: What's up?
Contr: Error: Drive controller timeout error

SCSI HDD Talking to SCSI Controller:
HDD: I'm gonna need more time for that write because I found a bad block
Contr: Yeah OK, go ahead and remap that bad boy
Contr: What's Up?
HDD: Need more time to map that bad block
Contr: Yeah OK, go ahead
HDD: All done, grabbing the next command in the queue

Re:SCSI RAID Yes, IDE RAID No (1, Informative)

Anonymous Coward | more than 9 years ago | (#13140874)

I should probably add that SATA is closer in terms of functionality to SCSI than PATA. This does NOT mean that all controllers support it, however.

Re:SCSI RAID Yes, IDE RAID No (0)

Anonymous Coward | more than 9 years ago | (#13140901)

Non Clueful Quip

Re:SCSI RAID Yes, IDE RAID No (1)

drsmithy (35869) | more than 9 years ago | (#13141074)

IDE drives have had sector remapping for _at least_ 10 years now.

Offset backups first, then RAID (1)

inflex (123318) | more than 9 years ago | (#13140782)

Personally, I prefer daily backups to another HDD (use rsync, it's great), that way, if I make a major *oops* during the day I know I have a very recent backup immediately available, this is something that RAID cannot protect you from (the human failure).

If then I've still got money to spare, I'll look at mirroring.

http://www.mikerubel.org/computers/rsync_snapshots / [mikerubel.org] is a great page to learn about using rsync to make easy backups.

Fact checking... (1)

KhaymanUCSD (801306) | more than 9 years ago | (#13140785)

Anyone else notice the error in the RAID 5 explanation?

Justification: (2, Funny)

lanced (795958) | more than 9 years ago | (#13140793)

Yes!!!! I now can point my PHB to this article, and then to the article on how to turn IPods into a raid, and that should be enough to convince him to buy a few dozen. Now I will just need to explain to him why having a spare Ipod stored at my house will be a wise decision, you know, just in case the vendor closes it doors tomorrow or does something 'crazy' like switch architectures next year.

There are two types of people: (2, Insightful)

caluml (551744) | more than 9 years ago | (#13140798)

There are two types of people: Those that have lost data, and those that will.

Don't forget, though kids - RAID won't protect you from deleting your own data, or a malformed script trashing stuff.

Re:There are two types of people: (1)

pete19 (874979) | more than 9 years ago | (#13140948)

RAID won't protect you from deleting your own data, or a malformed script trashing stuff.

Which is exactly why I prefer to use a DVD backup instead. I get free DVDs from my university, so I keep one backup in my flat in case I need it quickly and one at a friend's place for off-site storage. That way I'm also (more) protected from fire. If my machine goes up in flames it doesn't matter how many HDDs I have, they'll all be damaged, but at least with DVDs I can save my really important stuff.

Re:There are two types of people: (1)

gunpowda (825571) | more than 9 years ago | (#13140949)

Data Loss in PCs:

There are 10 types of people: oh, wait. What was I going to say?

I for one welcome our new... (0)

Anonymous Coward | more than 9 years ago | (#13140808)

... eh Raiders.

Seriously, can't we learn about how hot a redhead is in bed vs a blonde?

Simple (1, Insightful)

Mensa Babe (675349) | more than 9 years ago | (#13140812)

"Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens."

Why? That's actually quite simple. Losing consciousness once due to a brick falling on the head may be all that is required to convince anyone that a helmet is right for them, but we don't see people wearing helmets, do we? Do people wear bulletproof vests? No? Why not? After all the benefits of a bulletproof vest over an ordinary vest far outweigh the extra consideration required during installation! Please, people, could we stop being such naive children thinking that our beloved industry is somehow special, that ones and zeroes have more value than humen lives? Could we please stop being so pathetic once in our lives? RAID may be a nice idea for "nerds that matter" but it is not for grandma. Period.

Re:Simple (0)

Anonymous Coward | more than 9 years ago | (#13140972)

actually grandma is the one that neeeds RAID 5. She's not going to backup her data EVER. and she's going to use the same computer for 10 years instead of buying a new one every 2 years so she will experience a hard drive failure. and after she losses all her data she'll probobly just stop using the computer.


But if instead of that 160GB HD she has 3 40GB drives in a RAID 5 array when drive 1 fails she gets a dialog saying a drive has died, she calls up little jimmy from down the street to put in a new one, and then all is right with the world again.

Technology is useless if it is not reliable

Re:Simple (0)

Anonymous Coward | more than 9 years ago | (#13141001)

Could we please stop being so pathetic once in our lives?

Well, apparently you can't ...

I'd almost think the parent was a karma whoring post, but it's so absurdly stupid that I can't imagine anyone would be tricked into moderating it up.

mod u4 (-1, Flamebait)

Anonymous Coward | more than 9 years ago | (#13140827)

won't vote in on an endeavour won't vote in FreeBSD had long Paper towels, g'loves, condoms is the ultimate Posts. Therefore out how to make the

Simple (1)

varmittang (849469) | more than 9 years ago | (#13140873)

Choose your Raid [raid.com] Click on which type of raid you want to know about, and it tells you what its good for, disadvantages and advantages.

is it possible to mix raid iwith non raid? (1)

urbieta (212354) | more than 9 years ago | (#13140910)

Im thinking of adding a couple big disks to raid together for user files

And keep my small hard drive for the operating system, if OS dies Id like to restore its image from the raid array.

Am I dreaming here? or how can I do it? :D

Re:is it possible to mix raid iwith non raid? (0, Redundant)

woah (781250) | more than 9 years ago | (#13140975)

... raid array.

Isn't that a bit, you know... redundant.

Windows RAID Over Firewire - Registry Setting (4, Interesting)

meehawl (73285) | more than 9 years ago | (#13140911)

For those who have run out of internal space in their boxes, and who don't have external SATA or expensive hardware boxes, you can run RAID over Firewire.

The problem, however, is that out of the box Windows refuses to "promote" an external disk to dynamic, which is required on all post-NT4 rigs for RAID.

The solution is to add a semi-documented Registry flag, EnableDynamicConversionFor1394 [google.com] .

HOW TO: Convert an IEEE 1394 Disk Drive to a Dynamic Disk Drive in Windows XP [microsoft.com]

Couple that with a cheap 4-bay firewire JBOD box and any spare old enclosures and you are set!

I run 2TB in various RAID configs on my Windows server (main and near-line storage). Have done so since 2002. No problems with the external boxes. The support for external firewire RAID is a little gnarly in Windows 2000 - volume must be mounted as a named virtual directory and cannot be mounted as a letter drive. Later Windows give you both options.

RAID and Home PCs (2)

agsharad (303407) | more than 9 years ago | (#13140913)

With hardware cost falling steeply, when will it become viable for home users to start having RAID-based PCs?

All said and done, many of us do keep fairly important data on our home PCs. How many of us make an effort to back it up?

blah blah blah (0)

Anonymous Coward | more than 9 years ago | (#13140916)

RE:"Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens."

data backup is what CD Burners are for, well they are plenty good enough for me.

RAID 0+1 vs RAID 1+0 (2, Informative)

georgewilliamherbert (211790) | more than 9 years ago | (#13140930)

This is a non-trivial question:

When you're setting up a RAID set using both striping and mirroring, do you want to set up two stripes and then mirror between the stripes (0+1), or do you want to set up mirrored pairs and then stripe those mirrored pairs (1+0)?

This is a quiz, and your data will grade you.

What you want, by far, is RAID 10 (1+0).

When you set up two stripes and then mirror across them, if you lose two disks, any disk in the first stripe and any disk in the second stripe, you lose all the data.

If you stripe across mirrored pairs, then the only way to lose data is to lose both drives in one of the mirrored pairs. You can lose any other disk than the second drive in a pair, or even many more disks, as long as they aren't both in the same mirrored pairs.

This doesn't make a difference with 4 drives. At 6 drives and up, use 10. Your data and users will thank you for it.

We need new technology (1)

zymano (581466) | more than 9 years ago | (#13140934)

We need something other than harddrives. They are the slowest part of computers and they crash.

A laser/magneto drive would be more reliable and have more density ?

Re:We need new technology (1)

Armadni General (869957) | more than 9 years ago | (#13140987)

We have something other than harddrives. It's called memdisk.

And it's incredibly expensive.

nt (1)

Armadni General (869957) | more than 9 years ago | (#13140951)

I'm planning a 800 GB (4x400GB) RAID 10 array whenever I come up with $1200. Now, I'm a total RAID newb, but even after raiding that articlem I still didn't learn anything. I'll take the Wikipedia article [wikipedia.org] any day.

Not until a HDD failed on me... (2, Interesting)

Soulfarmer (607565) | more than 9 years ago | (#13140959)

I had my system hard drive fail fatally on me, emails and so forth, only some random backups elsewhere. Right then and there I decided that no more will a hdd failure steal my stuff from me and bought 4x120gb drives (size/price ratio at time was optimum) and a Promise controller. Now I got ca. 240gb RAID 01 setup, mirroring gives reduncancy and striping keeps the array at least as fast as those drives used separately.

One hdd did fail on that array, and I just replaced it with warranty replacement hdd. No hassle, just carefree usage.

The piece of mind is worth LOT more than those extra drives. I DO NOT like the menial job of building the OS from zero to working state, just because of a hardware failure, WHEN I can just as well avoid it.

Proability of a failure greater than zero (0) is not zero. And I like it to be zero.

Re:Not until a HDD failed on me... (1)

Armadni General (869957) | more than 9 years ago | (#13140973)

I'm actually a really big fan of RAID 10 instead of RAID 0+1. What made you go for 0+1?

Re:Not until a HDD failed on me... (1)

Soulfarmer (607565) | more than 9 years ago | (#13141021)

ummm.. not sure anymore. Not actually sure anymore which one I got. 01 or 10... with 4 disks, it doesn't really matter as long as only one drive fails before the array is rebuilt. Of course, if pair1 A and pair2 A drives fail at the same time, despair ensues, but if the two concurrently failing drives are A and B in their separate pairs, it is still rebuildable.

But I really don't remember if mine was RAID10 or not. Performance-wise, I am not sure which is better even..

RAID = Backup? (1)

pipingguy (566974) | more than 9 years ago | (#13140965)


A lot of motherboards come equipped with RAID capabilities even if the end user doesn't know what the acromym means.

Now that external USB/Firewire drives have become more affordable as a backup solution, I recommend that. Confession: I don't know WTF I am talking about.

Re:RAID = Backup? (1)

Spad (470073) | more than 9 years ago | (#13141007)

I don't know of any mainstream desktop boards that offer any more than 0/1/0+1, which is either unreliable (0) or inefficient (1/0+1).

RAID 5 is what you want, it's just bloody expensive to get it (in hardware) at the moment. If one of your drives fails, you just take it out, stick in a replacement and it will rebuild the array for you from the parity information on the other drives. Fast read/write and good redundancy.

Re:RAID = Backup? (1)

Packet Pusher (231564) | more than 9 years ago | (#13141049)

Until your raid controller fails and you realize that for no amount of money can you buy a replacement that will get your data back in any reasonable amount of time.

Wow, a whole story I disagree with! Hmm.... (1)

King_TJ (85913) | more than 9 years ago | (#13140989)

At one time, I thought RAID was teriffic. But honestly, I think it's way over-rated and exists primarily for the benefits of systems builders and manufacturers to sell people additional hardware and increase their profits.

1. RAID implementations on most consumer-grade motherboards (EIDE RAID with Promise controllers on-board, and so on) are cheezy. I've tried using them for several years now, and I ran into lots of unexplainable "glitches" that never occured when I took RAID out of the equation. (EG. The RAID array would suddenly report a failed drive, yet when I'd pull the drive out and try reformatting/reusing it on another machine as a stand-alone C: drive, it would have no problems at all and S.M.A.R.T. reported it was fine too.)

2. As others pointed out, the RAID controller is the new "single point of failure" - and amazingly, they do seem to go bad far more often than I'd expect for an expansion card on "better quality" RAID setups. I used to work for a place that slowly had every last one of their Dell "PERC II" RAID controllers die off, one by one, on their Poweredge servers - causing all kinds of hassle. (The card was no longer in production so finding identical matches for all the dead ones wasn't so quick or easy.)

3. If you buy both of your drives at the same time, from the same place, they likely came from the same production run - so if one drive gives out, there's quite a good chance your other one(s) in your array will follow within a short period of time. After all, both have been running for the exact same number of hours of operation, at identical temperatures inside the system. More than once, I've seen a drive fail in a mirrored set, and then the spare died before the user got a chance to swap out the first one. So much for the data....

4. If you actually get "hot swap" drive trays for your RAID system on a home-built PC, good luck with those too. Most of the ones I've purchased locally or over the net have been poor quality - creating yet another "point of failure". The cheap, little cooling fans in them usually wear out quickly, and I've had the little circuit/switch break on a couple that lets you put the key in and turn it to power the drive on/off to prepare it for removal/re-insertion.

Honestly, I think the only solution is a good backup to off-site media if you have really important data to keep. For many home users, this probably isn't even a huge deal. Throw your resume and important documents on a flash drive or CD-R/DvD-R disc, and if the rest ever crashes - it's a good excuse to do a fresh, clean OS re-install anyway.

Blu-Ray (1)

Jambon (880922) | more than 9 years ago | (#13140998)

With Blu-Ray and HD-DVD on the horizon, each offering 30-50 GB per disc and in some cases more at a fraction of the cost, why would a normal consumer need to backup stuff using a RAID array? You're going to need to replace the broken hard drive anyway. I can see RAID being useful for businesses where they want as little downtime as possible, but is there really any point in buying more hard drives when you can get the same effect with DVDs or the upcoming BluRay and HD-DVDs? You can cite performance as an advantage using RAID 0, but as has been shown [anandtech.com] , there really isn't any.

RAID is really here (2, Informative)

JB72 (463516) | more than 9 years ago | (#13141009)

It's amazing how common RAID is now, especially (S)ATA RAID.

In video editing, RAID is everything. External SATA RAID is the big thing now, and it works pretty well, even when it's OS based. What I haven't seen yet are (relatively) cheap SATA RAID 5 enclosures. That would be the Holy Grail of fast media storage.

RAID is just NOT reliable (1, Insightful)

Anonymous Coward | more than 9 years ago | (#13141035)

I've sold Entreprise hardware / software / projects for over 13 years, and the handful of catastrophic data losses / service interruption / nightmarish server setup / stability issues my clients have had have ALWAYS been with RAID systems.

Of course, if you're using RAID it's because you need capacity / speed / reliability, and while it seems the first two are indeed delivered, there is a HUGE reliability issue.

Back in the days when i was selling Dell's own RAID array (can't remember the name), it was well known at Dell that the controller software was buggy, they fired the programmer but still sold the stuff. And thing haven't improved since. A couple of years ago it took a Compaq high-end VAR several MONTHS to get multi-gig RAID5 setup working. My brother works for a very large company, and after months of problems, their SUN lead person admitted that SUN has issues with their RAID controllers, especiallly the replacement ones / spare parts. Remember when SETI@HOME went down for a week a couple of years ago ? SUN RAID controler problems !

My advice to clients is to avoid RAID whenever possible. Have spare servers, do very frequent backups, split your databases, have gobs of RAM... For the cost of a first-tier RAID system, you can buy a lot of other stuff, that WILL be useful in a lot more cases: fried servers, corrupted files... It's too bad the SCSI disks we use lag so much is capacity compared to ATA. I haven't done any SATA yet.

The one thing less reliable than RAID is clusters, BUT i haven't handled clusters in a while, i'm talking 5 years ago. May be the new Linux ones are better ;-) I have no real-life experience with FC and the thing over ethernet yet. i'm VERY leery of my customers being used as beta-testers / guinea pigs.

My 10 cents

Sorry for the "AC", but since I'm naming names ...

how do failures behave? (1)

mo (2873) | more than 9 years ago | (#13141056)

I've fiddled with raid a bit but haven't yet had enough failures under my belt to know how raid systems behave in real-world drive failures. Can somebody comment on their experiences for the following hardware configs:
  • What happens when, say, an IDE drive fails using software raid on linux? Does the machine stay alive, or do you need to remove the drive and reboot to get back to working?
  • How about failures with full hardware raid, like an LSI megaraid card. I've unplugged a drive with one of these and it beeps a lot, and seems to recover when they get plugged back in, but what about a true drive failure?
  • I'm also really curious about these new SATA raid controllers that libata calls "fake" raid controllers. Can they gracefully handle a disk crapping out?
TIA to anyone who's seen enough failures to comment on this.

Build or Buy? (1)

tabdelgawad (590061) | more than 9 years ago | (#13141062)

As a future project, I was thinking of building a RAID 5 solution from stock parts, but then I came across this

http://www.lacie.com/products/product.htm?pid=1032 6 [lacie.com]

Which seems not to be much more expensive than building your own. The same company has a nice line of other desktop and network drives (I have no connection to this company whatsoever).

Drawbacks?

Tommorrow the basics of RDMS (1)

jbplou (732414) | more than 9 years ago | (#13141064)

Seriously is this site about news or info you can find in books 15 years old?

RAID is way overhyped (1)

llZENll (545605) | more than 9 years ago | (#13141072)

Don't use stripping for performance unless you do video editing:
http://www.anandtech.com/storage/showdoc.aspx?i=21 01&p=10 [anandtech.com]

Don't use RAID0 for redundancy because its not worth the effort, you still have a single point failure of the raid controller card. Stick with a 2nd device (usb drives are good) which you simply copy your important data to every week or so.

Unless you can afford and need RAID5 (5 hard drives) forget about RAID and be happy your not wasting your time with it.
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