On 11/16/2016 3:35 PM, Wols Lists wrote:
On 16/11/16 09:04, Alexander Shenkin wrote:
Hello all,
As a quick reminder, my sdb failed in a 4-disk RAID5, and then sdc
failed when trying to replace sdb. I'm now trying to recover sdc with
ddrescue.
After much back and forth, I've finally got ddrescue running to
replicate my apparently-faulty sdc. I'm ddrescue'ing from a seagate 3TB
to a toshiba 3TB drive, and I'm getting a 'No space left on device
error'. Any thoughts?
One further question: should I also try to ddrescue my original failed
sdb in the hopes that anything lost on sdc would be covered by the
recovered sdb?
Depends how badly out of sync the event counts are. However, I note that
your ddrescue copy appeared to run without any errors (apart from
falling off the end of the drive :-) ?
Thanks Wol.
From my newbie reading, it looked like there was on 65kb error... but
i'm not sure how to tell if it got read properly by ddrescue in the end
- any tips? I don't see any "retrying bad sectors" (-) lines in the
logfile below...
username@Ubuntu-VirtualBox:~$ sudo ddrescue -d -f -r3 /dev/sdb /dev/sdc
~/rescue.logfile
[sudo] password for username:
GNU ddrescue 1.19
Press Ctrl-C to interrupt
rescued: 3000 GB, errsize: 65536 B, current rate: 55640 kB/s
ipos: 3000 GB, errors: 1, average rate: 83070 kB/s
opos: 3000 GB, run time: 10.03 h, successful read: 0 s ago
Copying non-tried blocks... Pass 1 (forwards)
ddrescue: Write error: No space left on device
# Rescue Logfile. Created by GNU ddrescue version 1.19
# Command line: ddrescue -d -f -r3 /dev/sdb /dev/sdc
/home/username/rescue.logfile
# Start time: 2016-11-15 13:54:24
# Current time: 2016-11-15 23:56:25
# Copying non-tried blocks... Pass 1 (forwards)
# current_pos current_status
0x2BAA1470000 ?
# pos size status
0x00000000 0x7F5A0000 +
0x7F5A0000 0x00010000 *
0x7F5B0000 0x00010000 ?
0x7F5C0000 0x2BA21EB0000 +
0x2BAA1470000 0x00006000 ?
In which case, you haven't lost anything on sdc. Which is why the wiki
says don't mount your array writeable while you're trying to recover it
- you're not going to muck up your data and have user-space provoke
further errors.
gotcha - i'm doing this with removed drives on a different (virtual)
machine. Seemed like the arrays were getting mounted read-only by
default when the disks were having issues...
If the array barfs while it's rebuilding, it's hopefully just a
transient, and do another assemble with --force to get it back again.
so, i guess i put the copied drive back in as sdc, and a new blank drive
as sdb, add sdb, and just let it rebuild from there? Or, do I issue
this command as appropriate?
mdadm --force --assemble /dev/mdN /dev/sd[XYZ]1
Once you've got the array properly back up again :-
1) make sure that the timeout script is run EVERY BOOT to fix the kernel
defaults for your remaining barracudas.
2) make sure smarts are enabled EVERY BOOT because barracudas forget
their settings on power-off.
3) You've now got a spare drive. If a smart self-check comes back pretty
clean and it looks like a transient problem not a dud drive, then put it
back in and convert the array to raid 6.
4) MONITOR MONITOR MONITOR
You've seen the comments elsewhere about the 3TB barracudas? Barracudas
in general aren't bad drives, but the 3TB model has a reputation for
dying early and quickly. You can then plan to replace the drives at your
leisure, knowing that provided you catch any failure, you've still got
redundancy with one dead drive in a raid-6. Even better, get another
Toshiba and go raid-6+spare. And don't say you haven't got enough sata
ports - an add-in card is about £20 :-)
Cheers,
Wol
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