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I'm setting up a RAID1 array of two new 4TB hard drives.

I heard somewhere previously, that making a RAID1 array of new identical hard drives bought at the same time, increased the chance that they would fail at a similar point in time.

I am therefore considering using one of the hard drives for a period of time (maybe a couple weeks) on its own, in an attempt to reduce the likelihood of both failing within a short amount of time. (the unused drive would be kept disconnected in a drawer)

Does this seem like a reasonable approach, or am I more likely just wasting my time?

a_henderson
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6 Answers6

16

It's a waste of time.

You won't be able to induce failure or stress the drives in a meaningful manner. You have RAID, and that's a good start. Just make sure you have monitoring in place to actually detect failures as they occur and backups to protect against disaster.

ewwhite
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5

It may be better to use different brands or series of disk together if you're worried about this.

I have seen disks of similar type and age fail in clusters, so IMHO it's not an urban leend.

wurtel
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2

Great Question - However, unlike automobile headlights, this is a waste of time. The MTBF [mean time between failures] rating for 4 GB drives [WD Red in this example] is 1,000,000 hours. The odds of two drives going bad in a mirror at the same time is extremely rare. When I have seen this happen, it is has been because the first drive failed without anyone noticing. More useful to protect with backups than to bother burning-in one drive first. If you do mix drive types, make certain the drives are the same speed. If you are paranoid, then RAID 10 is for you.

DocB
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While it makes sense in theory, the data doesn't support the need to work in your drive.
Not only will a few weeks not really make an impact, the failure percentages don't really work when looking at only two drives.

While there has been some indication of more normalized failure rates when it comes to drives of the same model.

Most age-related results are impacted by drive vintages... Interestingly, this does not change our conclusions. In contrast to age-related results, we note that all results shown in the rest of the paper are not affected significantly by the population mix. (emphasis mine)

As such, age related failures, which is only a small subset of failures, can be somewhat correlated to drive vintages. But the majority of failures can't.
If you add to this the overall failure percentages, which can peak at 8% for a given year, the odds of both drives failing in the same year are small, them failing in the same week is negligible.
And this is if you look at every possible cause of failure, not only age related failures.

If you want to minimize the risk, but two drives of a different vintage.
If you want assurances, buy an insurance.
And as ewwhite's answer already stated, backups and monitoring are a must.

Community
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Reaces
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This is usually an argument for SSDs more than HDDs in my experience. SSDs have limited write cycles, therefore if you use a RAID1 with two SSDs of the same model, both should run out of write cycles near the same time.

As for general failures, unless you have a serious issue like mass vibration, static, or high heat; I don't suspect you'll see 2 out of 2 drives fail at the same time.

A main concern with RAID1 (and RAID10) with larger drives like 4TB is the rebuild. With a 2 drive mirror, when one drive fails, the other drive is then carrying twice the work load. Then when you rebuild, that drive is getting even more load. If there was anything wrong with that drive, it is likely to fail in those conditions especially considering rebuilding a 4TB mirror under load can take a long time.

Devon
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You can do, but it won't help too much.

For example, if there is a needle in the input power, the same needle will kill both disks.

What is important: you need to have a good backup. Raid doesn't make up for a good backup. Actually, if you have a good backup, maybe a mirroring raid isn't surely needed (if you can tolerate a system collapse once around 2-3 years).

peterh
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