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Ask Slashdot: How Do You Test Storage Media?

georgewilliamherbert Re:Why? (297 comments)

Raid is toast. I dont care WHAT raid you are running, none of them can withstand a loss of 50% of the drives.

Really? I used to do that as a routine acceptance test for clusters. The only times it failed for real was when we'd screwed up something.

For that to work, you have to rigorously separate RAID mirrors into their own trays so that a whole tray failure (or cable, as you said) only takes one mirror down. For something like 10, 50, 60 you just make sure all of one side is on one array and all of the other on another (or if you have more than 2 arrays, that you separate them out into pairs with one used for one side and one for another).

Physical separation helps as well, so that you don't accidentally unplug A while starting servicing on B. That exact scenario is one of the canonical HA oopses.

more than 2 years ago
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Ask Slashdot: How Do You Test Storage Media?

georgewilliamherbert Re:Why? (297 comments)

Also: HARDWARE RAID CARDS.

I can't stress that enough. software and semi-software raid is a joke.

Not until the hardware fails and you need the data that was on there but not on the backup (or realized the backup failed a long time ago...).

For performance, yes, hardware is fastest. For reliability though, software RAID is better (hardware RAID can have interesting firmware version issues).

Old SAN / Cluster folks believe in belt+suspenders. I.e., often, use both.

Use Software RAID 1 across a couple of LUNs (or separate controllers / drive array stacks, for non-SAN environments). Build the LUNs with internal RAID (5, 6, hot spares, figure out your rebuild times, etc.)

Also - hugely common failure is that the operators aren't properly monitoring the underlying hardware RAID drive status. You need to know immediately when a drive fails even if there's RAID6 and a couple of hot spares in the array. When I worked for a VAR on clusters, I can't count the number of times I arrived and found that they'd had 2, 3, 4 failures nobody noticed, and were one more failure away from catastrophic data loss...

more than 2 years ago
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Ask Slashdot: How Do You Test Storage Media?

georgewilliamherbert Re:Why? (297 comments)

There is a very slight bathtub type curve - all numbers rounded, it's about 3% AFR in the first quarter (i.e. about 0.75% failures in first quarter) and 2% for drives in the 3-12 month range (i.e. about 1.5%). If I read the statistics presentation there right 33% of first year failures look to happen in the first quarter, which is detectable but minor initial higher rate. That's dwarfed by 1-2 year AFR (about 8%) and 2-3 year AFR (about 9%), but drops slightly after that.

They presented the AFRs rather than the culminative losses in an initial cohort per quarter/year, which would be slightly clarifying, but whichever way they did the analysis it's about like that.

more than 2 years ago
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Ask Slashdot: How Do You Test Storage Media?

georgewilliamherbert Re:Why? (297 comments)

I have worked for an OEM who installed about 30,000 drives a year; for end users with 10,000 drive environments, built out new 1,000 HDD and 600 SSD environments in the last year. I know all about static, having had the manufacturer-level training on how not to zap.

It's not just static. Some drives come with SMART errors (or bad blocks that matter), despite $MFGR assurances. Some of the failures develop in the factory and get shipped anyways as unlikely to get worse, some develop while being packaged or shipped or unpackaged. Run SMART data collection across hundred-drive collections (or thousands or more) and you get a lot of useful and scary info.

Also, there are well documented runs of drives - specific models, time ranges, factories involved etc - which all just blew up. Also happens to chips sometimes - I've been seriously bit by bad CPUs by Sun and Intel, support chips from several vendors. Also RAM going bad.

One prototype CPU literally melted the system down, all the plastic nearby inside the casing melted and puddled on the bottom of the case, the CPU label plastic was carbonized.

more than 2 years ago
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Cheaper, More Powerful Alternative To FPGAs

georgewilliamherbert Delay Lines (108 comments)

Mmmm.... 40+ years after going out of style as "Hopelessly Obsolete", Delay Lines return to the cutting edge.

more than 3 years ago
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Intel Replaces Consumer SSD Line, Nixes SLC-SSD

georgewilliamherbert Re:*SMOOTCH!* Buh-bye Enterprise! (165 comments)

Doubling lifespan that way requires that you only use half the disk capacity.

I have burned out a Major Name Brand SLC SSD with a high traffic OLTP DB in eight months. I have heard the same from Large Internet Companies which tested these for internal use. There are ongoing independent reliability expert studies in FAST, HOTDEP, other conferences which are uniformly highly skeptical of vendors' claims on SSD lifetime.

If you have not actually tested the drive out to six years service, run an accellerated pilot test unit out ahead of your main prod usage, to give you the canary warning.

more than 3 years ago
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Hard Disk Sector Consolidates Amid Uncertain Future

georgewilliamherbert Re:The tried & trusted will still rule the ser (237 comments)

I've tried to do large database server farm tests on modern enterprise SSDs with TRIM, the best wear load leveling, SLC, etc. They go "poof" at moderate (few months, for my loads) lifetimes.

IOPS x Lifetime / price is a metric I find useful. Unfortunately, it makes SSD look even worse than it does just on a price basis 8-(

more than 3 years ago
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Hard Disk Sector Consolidates Amid Uncertain Future

georgewilliamherbert Re:The tried & trusted will still rule the ser (237 comments)

Not really improved. I burned out a REALLY GOOD (best available) SLC SSD in 7 months with a mirrored production workload at a previous jobsite not that long ago.

Poof. All gone.

At the FAST conference, was yet another presentation on SSD lifetime burnout mechanisms, news not actually improving in the slightest so far on life. SLC is not good enough; MLC is toast in write-intensive apps.

Phase-change memory or one of the others, with millions of write cycles per bit, may pull this out, but Flash is not proving good enough for enterprises.

more than 3 years ago
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Espionage In Icelandic Parliament

georgewilliamherbert Re:Recovery Fairy Tales again (274 comments)

The Great Zero Challenge rules specifically exclude disassembly of the drive; all the bit-recovery mechanisms discussed in the literature require you to disassemble the drive and use custom heads to scan the surface magnetism map.

I.e., the contest is totally missing the point on what data recovery pros (i.e., the NSA and so forth) said they'd do if they had to scan disks to recover overwritten data.

It's hard to think of a less useful contest.

more than 3 years ago
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First Pictures of Chinese Stealth Fighter

georgewilliamherbert Re:Looks like a clone of the Northrop YF-23 (613 comments)

Oh? A plane with a single fuselage, fuselage front engine intakes, canards, a delta wing, resembles an aircraft with separate engine pods on a flat center section, underwing engine intakes, a V-tail?

There's nothing configurationally similar between those aircraft. Nothing.

There's a passing similarity with the FB-22 bomber proposal, but that didn't have canards, just a delta, and was never more than a paper proposal (no detailed design or prototype).

more than 3 years ago
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First Pictures of Chinese Stealth Fighter

georgewilliamherbert Re:Someone help me out here. (613 comments)

Far more likely its based on stolen US plans.

For what?

There is no US stealth fighter design with that size or characteristics.

more than 3 years ago
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China To Build Its Own Large Jetliner

georgewilliamherbert Re:Quality control? (332 comments)

The technology they used to get to space was 90+% Russian

Common fallacy - they bought a Soyuz and a lot of engineering time, and the vehicles are similar in configuration and concept, but the Chinese vehicles are essentially a whole new design and used nearly no Soyuz components other than the docking mechanism and imported space suits (I think that was it).

Looks similar doesn't mean design stolen from. Chinese engineers did most of the hard work on all of the hardware with those two noted exceptions.

The launch vehicle was all theirs.

more than 3 years ago
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China To Build Its Own Large Jetliner

georgewilliamherbert Re:What's the adage? (332 comments)

There are plenty of tax havens to go off to and live in, if you feel that way.

Problem is, none of them are a large, expanding, dynamic economy.

They exist for a reason, but modern economics does as well - it works, and it wins out over time at producing the most benefit for the most people (including the rich, who at times object to how it works, but who are far far FAR richer in the west than elsewhere...).

The current system is not entirely fair or reasonable by any one group's definitions of those terms, and certainly sucks in many ways. Welcome to the Real World. It sucks, but obviously less so than any other ideas we've tried so far. See similar observations about western democracy as a government model.

When you have a model that you can adequately explain and defend as holistically better, you'll get converts. I have yet to see any critic who can explain an alternate model in detail, because most of the critics don't understand economies well enough to design and engineer one. So give it your best shot. Perhaps you have the cojones than all the professional issue radicals and far-stream economics professionals lack, new ideas and the brains to link them into a system and the communications skills to explain it. Go for it!

But not on /.

more than 3 years ago
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China To Build Its Own Large Jetliner

georgewilliamherbert Re:What's the adage? (332 comments)

As far as I can tell, the "science" of economics has predicted exactly zero major economic events over the course of human history. Not a great track record. Not a source of confidence. Not a science, really.

Prediction of really dynamic events - the long term weather, economics, etc - is really hard.

What you can do, scientifically, is analyze how different factors affect each other over time. You can predict that conditions are ripe for a type of event (inflation, unemployment spike, a market bubble, recession, etc). You can predict the course of an economic shift based on inputs (bailouts, government investment, policy changes, money supply changes, consumer confidence and employment, etc).

Being able to say "The bond market? It's going to collapse on Tuesday," is really hard.

Chastising economists because the economy is too complicated for us to do mid to long term projections accurately yet is unreasonable. They understand at micro, intermediate, macro, and international levels. They can show interactions and trends and make useful predictions. But they can't model the whole thing on an ongoing basis.

more than 3 years ago
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US Couple Arrested For Transmitting Nuclear Secrets In Sting Operation

georgewilliamherbert Re:FTFA (372 comments)

The Wikipedia article is intentionally not useful for designing anything.

However, we do have an online textbook (at roughly upper-division engineering/physics college student difficulty level) on the subject:
    http://www.nuclearweaponarchive.org/Nwfaq/Nfaq0.html

In terms of what's been published online -

* There's a book with precise dimensional drawings and measurements on the Little Boy type Uranium gun type bomb. Not online, but purchasable at Amazon. It's not "a blueprint" but any competent draftsman / mechanical engineer could produce blueprints to build from, given the book.

* The dimensions and materials of all the layers of the Fat Man / Mark 1 type nuclear weapons are published in numerous sources. The precise shape of the lens in the outer layer has not been, though a rough back-of-the-envelope version of the equation for the lens shape is published. A precise and buildable lens shape would require someone with a fair talent in explosives engineering and shockwave engineering, especially someone aware of what the published equation left out, but the Fat Man design is fundamentally so brick-solid-simple that one could get the lens fairly imprecise and still have a functional weapon.

Some effort has gone into not actively publishing newer weapon design details in public. But that's not nearly the same as "they're not out". A number of more modern weapons are understood to at least close to the level Fat Man and Little Boy are. There are accurate internal component photos declassified for some weapons and parts. There are detailed hands-on descriptions of some parts, by people who worked on them. Check out the Wikipedia article on the B61 bomb, for example; the fission and fusion components were shown in a declassified film (but not the explosives to compress the fission parts).

more than 4 years ago
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US Couple Arrested For Transmitting Nuclear Secrets In Sting Operation

georgewilliamherbert Re:FTFA (372 comments)

Not for nuclear weapon design information. That's "Restricted Data", see DOE classification rules. Accessed with a DOD TS-CNWDI (Top Secret - Critical Nuclear Wepon Design Information) or DOE Q-clearance plus appropriate Sigma compartment clearances for the specifics you're looking at.

more than 4 years ago
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Data Deduplication Comparative Review

georgewilliamherbert Re:Um.. (195 comments)

No, it's not.

Differential backups are taking a single filesystem, seeing what changed (either at the file level (whole changed/updated/new files) or block level (changed blocks within files).

Block level deduplication is noticing that the storage appliance on which you back up 100 desktops and 10 servers has 50 copies of the same version of each data block in each Microsoft OS file from XP, 25 from Win 7, and 35 from Fedora, and only storing 1 copy of each of those blocks rather than 100 separate ones. It's returning those blocks to the usable storage pool and remapping without having to "compress" anything, not having to rewrite the backup data images, etc. It's just saying "This is block 3 of the binary for Internet Explorer 8, and I already have a copy of that", for each and every common block out there.

You still have to upload the blocks, and the system still needs to scan them to notice the duplication, but it's a lot more than "oh, compression".

more than 4 years ago
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Data Deduplication Comparative Review

georgewilliamherbert Re:Not enough products (195 comments)

Thirded. Data Domain (now part of EMC) really started the commercial use of this...

more than 4 years ago
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HP Backs Memristor Mass Production

georgewilliamherbert Re:layered in 3 dimensions...hmmm (116 comments)

The basic architecture should be cheap to fabricate in bulk. It's lines of wires, a layer running in one direction, a thin film of the memristive material, then a layer of wires on top running at right angles. Every intersection point is a bit.

DRAMs involve all sorts of careful operations to create a trench or stack, fill it with a capacitor, run the lines in and out, etc. Much more complicated on a per-bit basis. Many more things can go wrong. Memristors are pretty much the simplest to implement circuit element I've seen come along in a long long time.

The key questions are performance. How many write cycles can the fabbed chips survive before bits start going bad / getting stuck? Typical MLC fash is 10-100 thousand, very good SLC flash 100k to 1m cycles. This is not enough that you can ignore the write lifetime issues, and today's SSDs will wear out if written very actively over long periods of time.

Memristors (and Phase-Change RAM, and some of the other options out there for new non-volatile RAM) offer potentially very long life. But it's not clear if the produced chips will be 1m and up, 10m, 100m, or what.

At some point the device's overall lifetime is shorter than the wearout rate and you stop caring about wear leveling, etc. You just detect bit errors and map around them, and a few bit errors happen over device lifecycles. The wear leveling now used is a big deal on SSDs and a major factor in their performance (or not).

Also very important is how fast the chips are. Should be fast - you fire a short AC pulse down one word line, read the bits out the bit lines. Either the resistor resists or it doesn't. Word line enable transistor delays and read amp sensing delays of less than 10x transistor cycle time at a given fab size/process are likely, which is pretty good. Potentially this is faster than DRAM, more like SRAM, but not all fab / design approaches would get there (and not all potential fab processes).

Secondarily, how fast is a write cycle. SRAM writes very very quickly. DRAM reasonably quickly. Memristor? Should be fast, but there are current and material breakdown concerns.

Fundamentally, we need to see the chips. When we see chip spec sheets, it tells us how useful these are.

It could range from "replaces FLASH at certain densities or write life requirements" to "replaces all FLASH completely" to "replaces a lot of DRAM" to "becomes the only memory in use between CPU caches and hard disks". Potentially, it could be cheap enough to even replace hard disks.

We've had computers in recent memory (1980s, early 1990s) which were operating without all the data cache tiers we now have to deal with in computer architecture. Large chunks of computer architecture now is nearly all about efficiently managing the tiered data storage - CPU registers to CPU cache, CPU cache to main memory, main memory to disk. There are factors of 10 speed difference or more between each tier (more from DRAM to disk). Fast reliable nonvolatile RAM could flatten that all out a lot. FLASH isn't good enough due to write lifecycle limits. Memristors, if the performance comes in near the top of the possible range, could. Will they? I'm not working for HP or Hyundai, I don't know what they've got. I'm preparing for designing some systems which could flatten things, who knows if we'll actually get there with this tech. It could be a game changer, or it could be just another technology on the block.

more than 4 years ago
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Stupid Data Center Tricks

georgewilliamherbert Re:cascade failures (305 comments)

The sad part is, datacenter power people are now on the "avoid stranded power" trip trying to increase power efficiency (UPSes and PDUs running at 80% are much more efficient than those running at 50%). They don't seem to understand or be willing to provision to support one leg actually failing completely.

They're handling the "one server out of tens has a power supply failure on one leg" failure, but not the "the whole rack flips to only using B power due to X"...

more than 4 years ago

Submissions

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Last free IPv4 blocks allocation in progress

georgewilliamherbert georgewilliamherbert writes  |  more than 3 years ago

georgewilliamherbert (211790) writes "IANA has announced that the last two unrestricted IPv4 /8 network blocks were allocated today to APNIC. By preexisting agreement, to avoid timing concerns from putting any regional IP number registry at a relative disadvantage, the remaining 5 /8 blocks are now to be allocated immediately to the 5 RIRs, which will presumably happen very soon.

Though one can semantically argue whether the final 5 allocation or the last 2 free blocks represent the actual end of IANA's IPv4 allocation, today was a major milestone in the end of new IPv4 use and coming IPv6 future."

Link to Original Source
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Multiple fiber cuts in San Francisco area

georgewilliamherbert georgewilliamherbert writes  |  more than 5 years ago

georgewilliamherbert (211790) writes "Multiple news reports, mailing list posts, blogs, and tweets are pointing out two overnight acts of sabotage in the San Francisco Bay area, with long distance fiber network cables being cut in two locations in the early morning hours. The first cut, around 1:30 AM, is affecting landline and cell phone service and 911 calls in the communities of Morgan Hill, Gilroy, and parts of Santa Cruz counties, was on an AT&T fiber alongside Monterey Highway near Blossom Hill Road, in San Jose. A second cut, around 3:30 AM, in San Carlos, affected Sprint fiber and has significantly disrupted services at the 200 Paul datacenter in southern San Francisco.

Rumor says that this may be related to a AT&T communications workers contract having just expired — but no evidence has been published yet in the media, and this could be an intentional act of sabotage by someone unrelated to the company's workers.

Anyone experienced with fiber links has seen plenty of backhoes, and a few tunnel fires and the like. This is relatively unusual, however."

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