Re: Removing a failing drive from multiple arrays

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NeilBrown wrote:
On Thu, 19 Apr 2012 14:54:30 -0400 Bill Davidsen<davidsen@xxxxxxx>  wrote:

I have a failing drive, and partitions are in multiple arrays. I'm
looking for the least painful and most reliable way to replace it. It's
internal, I have a twin in an external box, and can create all the parts
now and then swap the drive physically. The layout is complex, here's
what blkdevtra tells me about this device, the full trace is attached.

Block device sdd, logical device 8:48
Model Family:     Seagate Barracuda 7200.10
Device Model:     ST3750640AS
Serial Number:    5QD330ZW
      Device size   732.575 GB
             sdd1     0.201 GB
             sdd2     3.912 GB
             sdd3    24.419 GB
             sdd4     0.000 GB
             sdd5    48.838 GB [md123] /mnt/workspace
             sdd6     0.498 GB
             sdd7    19.543 GB [md125]
             sdd8    29.303 GB [md126]
             sdd9   605.859 GB [md127] /exports/common
    Unpartitioned     0.003 GB

I think what I want to do is to partition the new drive, then one array
at a time fail and remove the partition on the bad drive, and add a
partition on the new good drive. Then repeat for each array until all
are complete and on a new drive. Then I should be able to power off,
remove the failed drive, put the good drive in the case, and the arrays
should reassemble by UUID.

Does that sound right? Is there an easier way?

I would add the new partition before failing the old but that isn't a big

If you were running a really new kernel, used 1.x metadata, and were happy to
try out code that that hasn't had a lot of real-life testing you could (after
adding the new partition) do
    echo want_replacement>  /sys/block/md123/md/dev-sdd5/state
(for example).

Then it would build the spare before failing the original.
You need linux 3.3 for this to have any chance of working.


I expect to try this in a real world case tomorrow. Am I so lucky that when rebuilding the failing drive will be copies in a way which uses a recovered value for the chunk if there's a bad block? And only if there's a bad block, so that possible evil on the other drives would not be a problem unless they were at the same chunk?

As soon as the pack of replacements arrives I'll let you know how well this worked, if at all.

Bill Davidsen<davidsen@xxxxxxx>
  We are not out of the woods yet, but we know the direction and have
taken the first step. The steps are many, but finite in number, and if
we persevere we will reach our destination.  -me, 2010

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