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Once upon a time, I was taught to spread drive orders for at least around six disks or so to at least two vendors, three vendors if there are more than 20 disks. Use the same make and model of disk, but source them from different places. When installing the disks, make sure each RAID array has a mix of disks from each of the sources.

The purpose, of course, is to prevent problems if the there's a bad lot of disks and the vendor just adds them to your shipment sequentially. This could result in multiple disks in the same RAID arrays failing at near the same time, which could mean data loss.

Is this still good guidance, or are most reasonable vendors (ie: not newegg, tiger direct, or amazon, that deal mainly with consumers) aware of the situation and now deal with it correctly? Is it dealt with at the manufacturer level (manufacturing runs are broken up before vendor delivery)? Is it something you have to ask for? Or am I just worrying too much?

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4 Answers 4

up vote 4 down vote accepted

Disks fail, and you typically want to get them from different batches to be safe. Once you get them you still want to run them for a few days or weeks to be sure to shake loose the problem disks.

I've had disks go bad as quickly as one or two days before (EMC disks) and I've had the same disks from that array last for years. To be safe I would mix and match or if you need to order from the same vendor spread the order out over a month or two so you get disks from different batches.

Am I insanely paranoid when it comes to disk failure? Yep sure am. Nothing worse than losing data.

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It's worth taking a look at Google's research on disk failures. They have a lot of disks and have collected the data and analysed it: labs.google.com/papers/disk_failures.pdf –  Stuart Woodward Oct 1 '11 at 10:04
    
Above PDF now found at research.google.com/archive/disk_failures.pdf –  Deebster Feb 27 '13 at 12:54
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I don't think that's necessary anymore; I think drive reliability has progressed to the point where you don't have to worry about this anymore. Besides, the way most of these large scale vendors (newegg, tiger, amazon, etc) work, the chances of you getting 6+ drives from the same manufacturing lot at the same time [has got to be] pretty slim.

This is all a matter of option of course; so as always, do what makes you comfortable. After all, if the RAID does fail, it's your tail. ;)

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I personally don't pay much heed to that kind of advice as I think it's a little bit of chicken little syndrome (the sky is falling). I certainly wouldn't want to intentionally mix drives from different manufacturers in the same RAID array. When you're replacing a failed member disk it's almost unavoidable but I wouldn't build it that way out of the gate.

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Not different manufactures: same manufacturer and model, but sourced from different re-sellers –  Joel Coel Sep 30 '11 at 19:57
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Oh, gotcha. I'm still not sure I would do that. The vendors are still probably selling drives from the same batch because the manufacturer is shipping 1,000 units of batch A to vendor 1 and 2,000 units of batch A to vendor 2, etc. As a test you could look up a particular drive at a few different vendors and see if there's anything in the specs that identifies the batches and compare them. –  joeqwerty Sep 30 '11 at 20:21
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Unfortunately, just spreading your order so it's not from one batch is not good enough anymore. The problems like the seagate 7200.11 drives bricking due to bad firmware cannot be avoided by ordering the same model from different batches. I'd say if you're worried about a bad batch, you'd better order hard drives from different manufacturers for your RAID.

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