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Basically I have two identical hard disks that are in perfect working order, they just don't have the vibration tolerance they need for the environment they are in. (I am making an educated guess that this is the cause). The disks are in RAID 1 configuration via md raid/linux software raid. The RAID is then partitioned with LVM.

The issue is that every few days, on one or other of the disks, 1-5 contiguous sectors will start throwing I/O errors, but hdparm --write-sector puts them back in working order without issue. The disk does not clock up reallocated or pending sectors in SMART, so I can only assume that it manages to successfully fix the original sectors.

What I would like to do, is find some way to have the raid automatically fall back to the other disk for a sector it can't read. Currently the errors end up reaching the file system level and corrupting it, sometimes very severely. It tends to snowball the longer it is left.

I am confident the disks are not on the brink of failure, as they have been operating in this scenario for just under 2 years. The issue appeared after approx 6 months.

I have tried the flag which prioritises writes to one disk (usually used on SSDs) on the more reliable disk to no avail. Is there anything else I can try? I'm prepared to try alternative filesystems such as btrfs if the built in raid is more robust. Intel onboard 'fake' raid is also available to me (H67 chipset), but I'm guessing it is poor in comparison. Replacing the disks is very infeasible, as the box is colocated in what may as well be a different country (I am in Northern Ireland, the box is in England).

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What is "the environment they're in"? An earthquake zone? – Michael Hampton Mar 24 '13 at 22:09
Not far off, I'm surprised they work at all with the amount of vibration generated by the fans in the 1u case they're in - it was completely unbelievable when I built it. I guess the anti vibration screws etc. they've got help a bit – Luke Foreman Mar 25 '13 at 6:23

So what will you do when one of these spinning disks actually fails?(as all spinning disks eventually do)
I'll tell you: You'll solve your problem.

When the first spinning disk 'fails' (wink wink, nudge nudge:) Have the failed disk replaced with an SSD. Once the raid rebuilds, have the second disk 'fail' and replace it with an SSD.
It's a little BOFH-ish, but it will work, and you'll be the hero.

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What if his disks are bigger than the biggest SSD available on the market? I think we're only just getting up to 1TB at quite a high cost while spinning disks are up to 4TB now. Better to go with an enterprise drive in that case. – Matt Mar 25 '13 at 0:50
@Matt SSDs fail too. It's not only spinning disks that have a finite lifespan. – HopelessN00b Mar 25 '13 at 12:40

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