Problems with "btrfs dev remove" of dead disk

Hi,

One of my drives died earlier in a fairly emphatic way in that not only did it show IO errors and got removed as a device by the kernel, but it was also making audible grinding/screeching noises until I hot unplugged it.

Feb 14 18:29:36 specialbrew kernel: [27576156.070961] ata6.15: SATA link up 3.0 Gbps (SStatus 123 SControl 0)
Feb 14 18:29:37 specialbrew kernel: [27576157.215312] ata6.00: hard resetting link
Feb 14 18:29:37 specialbrew kernel: [27576157.555369] ata6.00: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:37 specialbrew kernel: [27576157.560028] ata6.01: hard resetting link
Feb 14 18:29:38 specialbrew kernel: [27576157.915797] ata6.01: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:38 specialbrew kernel: [27576157.920591] ata6.02: hard resetting link
Feb 14 18:29:38 specialbrew kernel: [27576158.275759] ata6.02: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:38 specialbrew kernel: [27576158.280603] ata6.03: hard resetting link
Feb 14 18:29:38 specialbrew kernel: [27576158.603658] ata6.03: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:38 specialbrew kernel: [27576158.608844] ata6.04: hard resetting link
Feb 14 18:29:39 specialbrew kernel: [27576158.947805] ata6.04: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:39 specialbrew kernel: [27576158.953058] ata6.05: hard resetting link
Feb 14 18:29:39 specialbrew kernel: [27576159.291801] ata6.05: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:39 specialbrew kernel: [27576159.297143] ata6.06: hard resetting link
Feb 14 18:29:39 specialbrew kernel: [27576159.639850] ata6.06: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
Feb 14 18:29:39 specialbrew kernel: [27576159.645411] ata6.07: hard resetting link
Feb 14 18:29:40 specialbrew kernel: [27576159.971581] ata6.07: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:40 specialbrew kernel: [27576159.977251] ata6.08: hard resetting link
Feb 14 18:29:40 specialbrew kernel: [27576160.303533] ata6.08: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:40 specialbrew kernel: [27576160.310056] ata6.09: hard resetting link
Feb 14 18:29:40 specialbrew kernel: [27576160.635541] ata6.09: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:40 specialbrew kernel: [27576160.641371] ata6.10: hard resetting link
Feb 14 18:29:41 specialbrew kernel: [27576160.967639] ata6.10: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:41 specialbrew kernel: [27576160.973591] ata6.11: hard resetting link
Feb 14 18:29:41 specialbrew kernel: [27576161.299570] ata6.11: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:41 specialbrew kernel: [27576161.305670] ata6.12: hard resetting link
Feb 14 18:29:41 specialbrew kernel: [27576161.631589] ata6.12: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:41 specialbrew kernel: [27576161.637725] ata6.13: hard resetting link
Feb 14 18:29:42 specialbrew kernel: [27576161.963597] ata6.13: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:42 specialbrew kernel: [27576161.969538] ata6.14: hard resetting link
Feb 14 18:29:42 specialbrew kernel: [27576162.295657] ata6.14: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:42 specialbrew kernel: [27576162.303094] ata6.00: configured for UDMA/100
Feb 14 18:29:42 specialbrew kernel: [27576162.310674] ata6.01: configured for UDMA/100
Feb 14 18:29:42 specialbrew kernel: [27576162.317928] ata6.02: configured for UDMA/100
Feb 14 18:29:42 specialbrew kernel: [27576162.326589] ata6.04: configured for UDMA/100
Feb 14 18:29:42 specialbrew kernel: [27576162.337178] ata6.05: configured for UDMA/100
Feb 14 18:29:42 specialbrew kernel: [27576162.344438] ata6.06: configured for UDMA/100
Feb 14 18:29:43 specialbrew kernel: [27576163.607145] ata6.03: hard resetting link
Feb 14 18:29:44 specialbrew kernel: [27576163.935962] ata6.03: SATA link down (SStatus 0 SControl 320)
Feb 14 18:29:44 specialbrew kernel: [27576163.942835] ata6.03: limiting SATA link speed to 1.5 Gbps
Feb 14 18:29:49 specialbrew kernel: [27576168.939422] ata6.03: hard resetting link
Feb 14 18:29:49 specialbrew kernel: [27576169.264031] ata6.03: SATA link down (SStatus 0 SControl 310)
Feb 14 18:29:49 specialbrew kernel: [27576169.270519] ata6.03: disabled
Feb 14 18:29:49 specialbrew kernel: [27576169.276874] end_request: I/O error, dev sdh, sector 0
Feb 14 18:29:49 specialbrew kernel: [27576169.282908] btrfs_dev_stat_print_on_error: 965 callbacks suppressed
Feb 14 18:29:49 specialbrew kernel: [27576169.282929] ata6: EH complete
Feb 14 18:29:49 specialbrew kernel: [27576169.294246] BTRFS: bdev /dev/sdh errs: wr 125, rd 8, flush 1, corrupt 0, gen 0
Feb 14 18:29:49 specialbrew kernel: [27576169.300987] sd 5:3:0:0: rejecting I/O to offline device
Feb 14 18:29:49 specialbrew kernel: [27576169.307016] BTRFS: lost page write due to I/O error on /dev/sdh
Feb 14 18:29:49 specialbrew kernel: [27576169.312976] BTRFS: bdev /dev/sdh errs: wr 126, rd 8, flush 1, corrupt 0, gen 0
Feb 14 18:29:49 specialbrew kernel: [27576169.319049] ata6.03: detaching (SCSI 5:3:0:0)
Feb 14 18:29:49 specialbrew kernel: [27576169.319433] sd 5:3:0:0: rejecting I/O to offline device
Feb 14 18:29:49 specialbrew kernel: [27576169.319443] BTRFS: lost page write due to I/O error on /dev/sdh
Feb 14 18:29:49 specialbrew kernel: [27576169.319448] BTRFS: bdev /dev/sdh errs: wr 127, rd 8, flush 1, corrupt 0, gen 0
Feb 14 18:29:49 specialbrew kernel: [27576169.319521] sd 5:3:0:0: rejecting I/O to offline device
Feb 14 18:29:49 specialbrew kernel: [27576169.319523] BTRFS: lost page write due to I/O error on /dev/sdh
Feb 14 18:29:49 specialbrew kernel: [27576169.319526] BTRFS: bdev /dev/sdh errs: wr 128, rd 8, flush 1, corrupt 0, gen 0
Feb 14 18:29:49 specialbrew kernel: [27576169.426264] sd 5:3:0:0: [sdh] Synchronizing SCSI cache
Feb 14 18:29:49 specialbrew kernel: [27576169.432734] sd 5:3:0:0: [sdh]  
Feb 14 18:29:49 specialbrew kernel: [27576169.438653] Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
Feb 14 18:29:49 specialbrew kernel: [27576169.444590] sd 5:3:0:0: [sdh] Stopping disk
Feb 14 18:29:49 specialbrew kernel: [27576169.450961] sd 5:3:0:0: [sdh] START_STOP FAILED
Feb 14 18:29:49 specialbrew kernel: [27576169.456838] sd 5:3:0:0: [sdh]  
Feb 14 18:29:49 specialbrew kernel: [27576169.462622] Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
Feb 14 18:30:21 specialbrew kernel: [27576201.178630] BTRFS: bdev /dev/sdh errs: wr 128, rd 8, flush 2, corrupt 0, gen 0
Feb 14 18:30:21 specialbrew kernel: [27576201.309583] BTRFS: lost page write due to I/O error on /dev/sdh
Feb 14 18:30:21 specialbrew kernel: [27576201.315761] BTRFS: bdev /dev/sdh errs: wr 129, rd 8, flush 2, corrupt 0, gen 0
Feb 14 18:30:21 specialbrew kernel: [27576201.322086] BTRFS: lost page write due to I/O error on /dev/sdh

…and those BTRFS: messages continue now even though the system no longer has a /dev/sdh.

Now:

$ sudo btrfs fi sh /srv/tank
Label: 'tank'  uuid: 472ee2b3-4dc3-4fc1-80bc-5ba967069ceb
        Total devices 6 FS bytes used 1.57TiB
        devid    3 size 1.82TiB used 383.00GiB path /dev/sdg
        devid    4 size 1.82TiB used 384.00GiB path /dev/sdf
        devid    5 size 2.73TiB used 1.25TiB path /dev/sdk
        devid    6 size 1.82TiB used 347.00GiB path /dev/sdj
        devid    7 size 2.73TiB used 464.00GiB path /dev/sde
        *** Some devices missing
$ sudo btrfs dev usage /srv/tank
/dev/sde, ID: 7
   Device size:             2.73TiB
   Data,RAID1:            464.00GiB
   Unallocated:             2.28TiB

/dev/sdf, ID: 4
Device size: 1.82TiB
Data,RAID1: 383.00GiB
Metadata,RAID1: 1.00GiB
Unallocated: 1.44TiB

/dev/sdg, ID: 3
Device size: 1.82TiB
Data,RAID1: 382.00GiB
Metadata,RAID1: 1.00GiB
Unallocated: 1.45TiB

/dev/sdh, ID: 2
Device size: 0.00B
Data,RAID1: 383.00GiB
Metadata,RAID1: 1.00GiB
System,RAID1: 32.00MiB
Unallocated: 1.44TiB

/dev/sdj, ID: 6
Device size: 1.82TiB
Data,RAID1: 347.00GiB
Unallocated: 1.48TiB

/dev/sdk, ID: 5

   Device size:             2.73TiB
   Data,RAID1:              1.25TiB
   Metadata,RAID1:          3.00GiB

System,RAID1: 32.00MiB
Unallocated: 1.48TiB

So, ideally I'd like to remove the missing device sdh (id 2) to have redundant copies of the data until I can insert a new drive. But "remove" doesn't seem to want to work:

$ sudo btrfs dev remove /dev/sdh /srv/tank
ERROR: not a block device: /dev/sdh
$ sudo btrfs dev remove 2 /srv/tank
ERROR: not a block device: 2
$ btrfs --version
btrfs-progs v4.4

I expect my kernel might be too old as it is a Debian backports version on wheezy (linux-image-3.16.0-0.bpo.4-amd64 3.16.7-ckt20-1+deb8u3~bpo70+1).

If I upgrade the kernel then should one of those remove commands above work?

I would rather not reboot just now if I can achieve redundancy in some other way. Would a rebalance like:

$ sudo btrfs balance -f -v -sdevid=2 -mdevid=2 /srv/tank

reconstruct redundant copies elsewhere?

With this btrfs-progs and kernel version, will a later "btrfs replace start -r /dev/sdh /dev/sdl" work without me rebooting into a newer kernel, even though /dev/sdh doesn't exist as a device to the kernel right now?

Any information/advice appreciated.

Cheers,
Andy

Since now it's a missing device, it should be

sudo btrfs device remove missing /srv/tank

But I'm not sure if this works when the volume is not already mounted degraded. There is no automatic degraded mechanism yet. I think even newer than 4.4 is needed plus a patch.

http://www.spinics.net/lists/linux-btrfs/msg51912.html

On the one hand, the rebuild doesn't change any fs features and therefore a device rebuilt with e.g. kernel 4.4, should then read fine later if you go back to 3.16. On the other hand, there's hundreds of bug fixes, many thousands of insertions and deletions in Btrfs since then, so it really doesn't make sense to me you'd want to increase risk of more Btrfs problems when such known things are now fixed. Consider 4.1.15 if you want a stable long term yet currently supportable kernel.

Chris Murphy

Hi Chris,

$ sudo btrfs device remove missing /srv/tank
ERROR: error removing device 'missing': no missing devices found to remove

I have now done:

# mount -oremount,degraded /srv/tank 

and tried again, but it produces the same response ("mount" now does show "degraded" as one of the mount flags, however).

I have not yet tried completely unmounting it and mounting it again.

It is inconvenient to reboot just now, so if I'm able to fix things without doing so (e.g. by balance or replace) then I would like to.

If that won't be possible then I will of course boot into a newer kernel at the same time.

If I end up booting into 4.1.15 then it should be possible to mount degraded and remove missing?

Cheers,
Andy

You need the patch set
[PATCH 00/15] btrfs: Hot spare and Auto replace

which includes the patch required here.
[PATCH 07/15] btrfs: introduce device dynamic state transition to
offline or failed

and this will take care of stopping the IO when disk fails.

btrfs progs has a code to fabricate missing in the user land instead of obtaining from the kernel.
---
commit 206efb60cbe3049e0d44c6da3c1909aeee18f813
btrfs-progs: Add missing devices check for mounted btrfs.
---

So I recommend to use 'btrfs fi show -m', which I guess in your case shall not show that devid 2 is missing. Because without the kernel patch
[PATCH 07/15] btrfs: introduce device dynamic state transition to
offline or failed
Kernel won't make that (online to offline/failed) transitions at all.

Current workaround to tell kernel that a device is missing is only by .. unmount and mount (not remount (bug)) which is a kind of (enterprise unacceptable) workaround. Sorry about that.

::

Yep kernel does not know that device is missing. That part of the code is in the patch to be integrated as above.

Since now device is removed. So only option is to use devid if you want to remove/delete. but it needs the patch.
[PATCH 0/7] Introduce device delete by devid
I think this is being integrated into 4.5.x (needs both kernel and progs patches).

If you happen to try any of these patches, please consider to post results.

No. Please don't do that. It would aggravate the IO errors and disk will never be removed from the kernel.

I suggest reboot if its btrfs root or btrfs is not a kernel module, otherwise
umount
modprobe -r btrfs (removes stale device entries)
btrfs dev scan
mount

Now 'btrfs fi show -m' should show device id 2 missing. So now either you may replace devid2 or delete devid 2 based on your business data protection needs.

Kindly note. If you are trying the hot spare and auto replace patches, in this context after the reboot, the device id will be identified as missing. And Not failed. So the auto replace won't trigger the replace if you have a spare device. This is as designed.

Yes you can consider this, without needing to reboot, however the command will be
btrfs replace start -r 2 /dev/sdl /btrfs

Thanks, Anand