On 2017-11-14 03:36, Klaus Agnoletti wrote:
Hi list
I used to have 3x2TB in a btrfs in raid0. A few weeks ago, one of the
2TB disks started giving me I/O errors in dmesg like this:
[388659.173819] ata5.00: exception Emask 0x0 SAct 0x7fffffff SErr 0x0 action 0x0
[388659.175589] ata5.00: irq_stat 0x40000008
[388659.177312] ata5.00: failed command: READ FPDMA QUEUED
[388659.179045] ata5.00: cmd 60/20:60:80:96:95/00:00:c4:00:00/40 tag
12 ncq 1638
4 in
res 51/40:1c:84:96:95/00:00:c4:00:00/40 Emask 0x409 (media error) <F>
[388659.182552] ata5.00: status: { DRDY ERR }
[388659.184303] ata5.00: error: { UNC }
[388659.188899] ata5.00: configured for UDMA/133
[388659.188956] sd 4:0:0:0: [sdd] Unhandled sense code
[388659.188960] sd 4:0:0:0: [sdd]
[388659.188962] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[388659.188965] sd 4:0:0:0: [sdd]
[388659.188967] Sense Key : Medium Error [current] [descriptor]
[388659.188970] Descriptor sense data with sense descriptors (in hex):
[388659.188972] 72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
[388659.188981] c4 95 96 84
[388659.188985] sd 4:0:0:0: [sdd]
[388659.188988] Add. Sense: Unrecovered read error - auto reallocate failed
[388659.188991] sd 4:0:0:0: [sdd] CDB:
[388659.188992] Read(10): 28 00 c4 95 96 80 00 00 20 00
[388659.189000] end_request: I/O error, dev sdd, sector 3298137732
[388659.190740] BTRFS: bdev /dev/sdd errs: wr 0, rd 3120, flush 0,
corrupt 0, ge
n 0
[388659.192556] ata5: EH complete
Just some background, but this error is usually indicative of either
media degradation from long-term usage, or a head crash.
At the same time, I started getting mails from smartd:
Device: /dev/sdd [SAT], 2 Currently unreadable (pending) sectors
Device info:
Hitachi HDS723020BLA642, S/N:MN1220F30MNHUD, WWN:5-000cca-369c8f00b,
FW:MN6OA580, 2.00 TB
For details see host's SYSLOG.
And this correlates with the above errors (although the current pending
sectors being non-zero is less specific than the above).
To fix it, it ended up with me adding a new 6TB disk and trying to
delete the failing 2TB disks.
That didn't go so well; apparently, the delete command aborts when
ever it encounters I/O errors. So now my raid0 looks like this:
I'm not going to comment on how to fix the current situation, as what
has been stated in other people's replies pretty well covers that.
I would however like to mention two things for future reference:
1. The delete command handles I/O errors just fine, provided that there
is some form of redundancy in the filesystem. In your case, if this had
been a raid1 array instead of raid0, then the delete command would have
just fallen back to the other copy of the data when it hit an I/O error
instead of dying. Just like a regular RAID0 array (be it LVM, MD, or
hardware), you can't lose a device in a BTRFS raid0 array without losing
the array.
2. While it would not have helped in this case, the preferred method
when replacing a device is to use the `btrfs replace` command. It's a
lot more efficient than add+delete (and exponentially more efficient
than delete+add), and also a bit safer (in both cases because it needs
to move less data). The only down-side to it is that you may need a
couple of resize commands around it.
klaus@box:~$ sudo btrfs fi show
[sudo] password for klaus:
Label: none uuid: 5db5f82c-2571-4e62-a6da-50da0867888a
Total devices 4 FS bytes used 5.14TiB
devid 1 size 1.82TiB used 1.78TiB path /dev/sde
devid 2 size 1.82TiB used 1.78TiB path /dev/sdf
devid 3 size 0.00B used 1.49TiB path /dev/sdd
devid 4 size 5.46TiB used 305.21GiB path /dev/sdb
Btrfs v3.17
Obviously, I want /dev/sdd emptied and deleted from the raid.
So how do I do that?
I thought of three possibilities myself. I am sure there are more,
given that I am in no way a btrfs expert:
1)Try to force a deletion of /dev/sdd where btrfs copies all intact
data to the other disks
2) Somehow re-balances the raid so that sdd is emptied, and then deleted
3) converting into a raid1, physically removing the failing disk,
simulating a hard error, starting the raid degraded, and converting it
back to raid0 again.
How do you guys think I should go about this? Given that it's a raid0
for a reason, it's not the end of the world losing all data, but I'd
really prefer losing as little as possible, obviously.
FYI, I tried doing some scrubbing and balancing. There's traces of
that in the syslog and dmesg I've attached. It's being used as
firewall too, so there's a lof of Shorewall block messages smapping
the log I'm afraid.
Additional info:
klaus@box:~$ uname -a
Linux box 3.16.0-4-amd64 #1 SMP Debian 3.16.43-2+deb8u5 (2017-09-19)
x86_64 GNU/Linux
klaus@box:~$ sudo btrfs --version
Btrfs v3.17
klaus@box:~$ sudo btrfs fi df /mnt
Data, RAID0: total=5.34TiB, used=5.14TiB
System, RAID0: total=96.00MiB, used=384.00KiB
Metadata, RAID0: total=7.22GiB, used=5.82GiB
GlobalReserve, single: total=512.00MiB, used=0.00B
Thanks a lot for any help you guys can give me. Btrfs is so incredibly
cool, compared to md :-) I love it!
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