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I'm about to purchase a SATA hard drive. I was wondering if, aside from the storage capacity, are there any other factors I should keep in mind? I care above all about reliability. Is a more expensive drive less error-prone than a low-end one?

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There have been some bad models (not makes), like the IBM Deskstar 75GXP aka Deathstars (which led to IBM selling its HDD business to Hitachi) and the Maxtor DiamondMax 9/10 (the ones made in Thailand, and not Japan, IIRC), which had a lot of failures. –  paradroid Jun 11 '11 at 16:01
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4 Answers

up vote 13 down vote accepted

The "enterprise" or "server" drives are more expensive, but have higher estimated MTBF as compared to "consumer" drives. They use higher quality parts. If you compare only "consumer" drives than some price differential really won't tell you much. You usually don't find "enterprise" drives in stores. You usually find them as OEM drives that you can order online or from certain suppliers.

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Thanks, this was the answer I was looking for! However, I'm comparing the Seagate enterprise product line with their more affordable Barracuda series, and the latter has a lower annual failure rate than the former... what. –  vemv Jun 11 '11 at 16:29
    
Isn't it possible that "consumer" drives compare failure rate in typical consumer usage patterns, while enterprise drives are supposed to run 24/7? –  che Jun 11 '11 at 22:10
    
If you read the warranty the consumer drives are often only warranted for intermittent use, as well. –  Keith Jun 12 '11 at 0:09
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Meh. From my experience, the only real difference lies in the enterprise support and warranty: so when the disk breaks, enterprise support doesn't hassle you with two hours of "did you actually plug it into the computer?" and "did you try turning it off and on again?"; instead, you get a replacement disk on next business day. As for MTBF, that's just a marketing number IMNSHO ("um, yes, two of our disks broke down within two weeks, but it's not our fault (but we will replace them): the other six disks you have and all our disks that you can't see, they all actually work! MTBF! MTBF!"). –  Piskvor Jun 12 '11 at 12:12
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To be fair, I recently needed to activate the warranty for a Seagate Barracuda HDD, and they asked me no questions whatsoever. I went to their site, filled an RMA form, sent the drive, and got a new one 3 days later. –  danielkza Jun 21 '11 at 23:25
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If you have the time, read Pinheiro et al (2007) Failure Trends in a Large Disk Drive Population. Proceedings of the 5th USENIX Conference on File and Storage Technologies, Feb 2007. It can be retrieved from http://static.googleusercontent.com/external_content/untrusted_dlcp/labs.google.com/en//papers/disk_failures.pdf

In general, drives of the same manufacturer are make to the same specification in terms of the disk assembly. It is usually the tolerances that differs. To give an example, if you want a paper circle of 5cm diameter, a circle of 4.5 or 5.5 cm maybe acceptable for one use (e.g. home use for decoration of child's room) but a circle of 5.0cm, add or subtract 1mm, (i.e. within 4.9 - 5.1 cm) would be required if it is a decoration project for a project launch for some big, big company.

For example, the load/unload cycle specification of a home drive may be ~ 300,000 times, the load/unload specification of an enterprise drive would be ~ 600,000 times, doubling the figures. The tighter specification also applies to the drive assembly and the disk manufacturing process - and thus the non-recoverable read error rate would be much smaller for enterprise drives, for example, a typical, current home drive - Caviar Black (from Western Digital) would have a nonrecoverable read error per 10^14 bit read. Compare with a typical harddrive manufactured towards datacenter servers WD RE SAS, which would have a nonrecoverable read error per 10^15 bit read. Whether that 10 times more reliability matters to you, is another matter.

To be honest, how you use the drive, is likely more important than which drive you use. Below is a summary of google's findings:

  • 6-7% of the drives fail within first year of use. Within which, more than half of these failing drive will fail within 6 month. These drives tends to be utilized highly during these periods.
  • Failure of the drive follow a double peak model. The first peak is within 3 months, and the second peak is around 3 years.
  • After the first year, there is in general a 8% failure rate of harddrive annually.
  • The effect of temperature is twofold: [1] The lowest failure rate is seen at disks run around 40 degree C. [2] As the drive ages, the failure rate rises expoentially with temperature at third year. To interpret this statement, running the drive at ~35C would achieve the best compromise of longevity and early failures, and if your harddrive can be replaced every 2 years, running the drives as hot as 45C in general would in fact decrease the failure rate, but past the second year there will be an exponential increase if you shall run it at 45C.
  • If you use SMART reporting software (a nice one is Crystal Disk Info URL: http://crystalmark.info/software/CrystalDiskInfo/index-e.html ), if you see one scan error, 10% will fail within days, and 30% of the drive will fail within 6 months. Thus, backup and discard the drive accordingly after you see the first one. If you see a reallocation event, 10% will fail within ~4 months. Note, however that only 60% of all harddrive failures would be predicted by SMART system.

Update

MTBF
Mean time between failures is basically not very useful for the typical consumers. The Mean time between failure is usually ideal and theoretical. Let's say we have 500,000 drives with MTBF of 500,000 hours - if you run each and every of them together you will likely to have one of them failing every hour, statistically speaking, if you run them within their specification (temperature, humidity, power supply quality...) With reference to the google study, the realistic useful life of a harddrive would be more like 2 years (in a non-redundant system) or 3 years (in a redundant system) - if you use it 24 hours a day - In a redundant system (e.g. a RAID-[5,6]) you can lose a harddrive without losing data. Particularly, in RAID 6 you can lose a harddrive and still have redundancy during the rebuild process.

Service life
One often see some manufacturer quoting service life such as '5 years' and then offering you a warranty of '3 years'. Translation: "We believe that it should last some 5 years. If it fails within the first three years of use, we'll replace it at our cost, but if you have it failed between 3rd and 5th year, poor you. It certainly won't be the case that we have installed some sort of time bomb to make them unusable by its fifth birthday, but you should get a new harddisk and use instead of this 5-year-old harddrive if your data is any precious."

That's how they define it as I understood.

Last but not least, try reading the google paper, it's an excellent read.

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Apparently I typed too long an answer to have it accepted :'( –  bubu Jun 11 '11 at 16:07
    
You got a bunch of upvotes though :) thanks for the effort. Although I just wanted help for picking a model, this too is relevant to my interests. –  vemv Jun 11 '11 at 16:32
    
@bubu: +1 awesome answer. :) –  Mehrdad Jun 11 '11 at 17:17
    
Great answer, eager for the update :P –  Matthew Read Jun 11 '11 at 18:27
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You are correct about MTBF. The correct usage of that metric is to determine what quantity of disks to keep on hand to replace failures for large installations. This article by Seagate explains how MTBF came to be used, what it means, and how it should be understood. The best explanation is it's used to answer the question "how many disks should I keep on hand to replace failed disks?" which is an important question for server farms. –  Bacon Bits Jun 12 '11 at 9:46
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Are all basic SATA drives equally reliable?

No. Sata is just an interface to a hard disk and most reliability issues with hard disks is related to the actual hard disk and not the interface.

Is a more expensive drive less error-prone than a low-end one?

Not necessarily. Sometimes you are paying for the brand name, sometimes for the storage capacity, sometimes for access times (eg AV drives)

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I know SATA is just the interface - I just tought it would make my question more specific. So aren't there models that claim to have lower error rates? –  vemv Jun 11 '11 at 15:54
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You would hope that a more expensive drive would be made from higher quality components - however, as with all things, that isn't necessarily the case.

Personally I'd go for a brand I recognised, from a supplier I'd trust to replace it if it failed. Computer components tend to fail in one of two ways. Either when you first install them or at the end of a long(ish) life. If you've got a good returns policy to back you up then you've got the first situation covered.

Check the reviews of the ones you are considering. If they're OK products you won't find many, if it's a poor product then you will find people complaining - that's human nature. So the lack of good reviews isn't a bad thing, but the lack of bad reviews is a good thing.

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