Re: How to handle a RAID5 arrawy with a failing drive?

Marc MERLIN
2014-03-17T00:51:56Z

On Sun, Mar 16, 2014 at 05:23:25PM -0600, Chris Murphy wrote:
>
> On Mar 16, 2014, at 5:17 PM, Marc MERLIN <marc@merlins.org> wrote:
>
> > - but no matter how I remove the faulty drive, there is no rebuild on a
> > new drive procedure that works yet
> >
> > Correct?
>
> I'm not sure. From what I've read we should be able to add a device to raid5/6, but I don't know if it's expected we can add a device to a degraded raid5/6. If the add device succeeded, then I ought to be able to remove the missing devid, and then do a balance which should cause reconstruction.
>
> https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg30714.html

Thanks for the link, that's what I thought I read recently.

So, on 3.14, I can confirm
polgara:/mnt/btrfs_backupcopy# btrfs replace start 3 /dev/sdm1 /mnt/btrfs_backupcopy
[68377.679233] BTRFS warning (device dm-9): dev_replace cannot yet handle RAID5/RAID6

polgara:/mnt/btrfs_backupcopy# btrfs device delete /dev/mapper/crypt_sde1 `pwd`
ERROR: error removing the device '/dev/mapper/crypt_sde1' - Invalid argument
and yet
Mar 16 17:48:35 polgara kernel: [69285.032615] BTRFS: bdev /dev/mapper/crypt_sde1 errs: wr 805, rd 4835, flush 0, corrupt 0, gen 0
Mar 16 17:48:35 polgara kernel: [69285.033791] BTRFS: lost page write due to I/O error on /dev/mapper/crypt_sde1
Mar 16 17:48:35 polgara kernel: [69285.034379] BTRFS: bdev /dev/mapper/crypt_sde1 errs: wr 806, rd 4835, flush 0, corrupt 0, gen 0
Mar 16 17:48:35 polgara kernel: [69285.035361] BTRFS: lost page write due to I/O error on /dev/mapper/crypt_sde1
Mar 16 17:48:35 polgara kernel: [69285.035943] BTRFS: bdev /dev/mapper/crypt_sde1 errs: wr 807, rd 4835, flush 0, corrupt 0, gen 0

So from here, it sounds like I can try:
1) unmount the filesystem
2) hope that remounting it without that device will work
3) btrfs device add to recreate the missing drive.

Before I do #1 and get myself in a worse state than I am (working
filesystem), does that sound correct?

(again, the data is irrelevant, I have a btrfs receive on it that has
been running for hours and that I'd have to restart, but that's it).

Thanks,
Marc
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