Write-read errors, Raid1 recovery?

Solution 1:

You need to remove each hard drive, and test them with a tool like Seatools seperately.

http://www.seagate.com/www/en-us/support/downloads/seatools

One of the disks is likely going bad, but with RAID1, there is no way for the computer to know for certain which disk has good data on it, and which disk has bad data on it. If you're very unlucky, both disks will be going bad, but more than likely, it's just one of them.

In a RAID 1 configuration, there is no Master/Slave, the two disks become one, and everything is controlled via the Raid Controller. Because of this, you'll likely want to test the drives in a different machine. Also, if the tests come back with one disk bad, all you need to do is remove the old drive, and get a replacement soon. If you have RAID1, then the computer will run with only 1 drive.

Solution 2:

In theory you should be able to just pop out a drive on a mirrored array while the system is running, and it should keep running fine. I actually did this once (by accident I hasten to add) and there were no ill effects (aside from missing one of the mirrored pair, of course).

Very very risky on a live system though, so my recommendation here is to get a replacement in place NOW, and get as much data as possible transferred over to it, with the old server then being taken offline. The worst you can do is wait until it fails before taking action.

Having done that you will have established a position where most of your stuff is up and running and available to users. So then - and only then - you can start experimenting with the old box and seeing how much of the rest you can get back.

My suggestion of popping the drive is one way - pop a drive while running and check the data. If you get corruptions you know that the other one is good, if you don't you know that this one is good.

I would definitely not do anything that involved reboots of that system as the whole thing could fail to come back up at any point. If you've ever been in that position you know how unpleasant it is.

Solution 3:

Is it a hardware RAID controller? Most have a utility that you can use to check the health of your disks and which one may be degraded. The manufacturer will also provide a recommended procedure to replace the degraded drive and to rebuild the mirror.

Cheers