Hi Neil,
can you please let me know what have you decided after/whether you had
time to think about this issue.
Thanks,
Alex.
On Tue, May 28, 2013 at 4:16 AM, NeilBrown <neilb@xxxxxxx> wrote:
> On Mon, 27 May 2013 13:05:34 +0300 Alexander Lyakas <alex.bolshoy@xxxxxxxxx>
> wrote:
>
>> Hi Neil,
>> It can happen that a spare has a higher event count than a in-array drive.
>> For exampe: RAID1 with two drives is rebuilding one of the drives.
>> Then the "good" drive fails. As a result, MD stops the rebuild and
>> ejects the rebuilding drive from the array. The failed drive stays in
>> the array, because RAID1 never ejects the last drive. However, the
>> "good" drive fails all IOs, so the ejected drive has a larger event
>> count now.
>> Now if MD is stopped and re-assembled, mdadm considers the spare drive
>> as the chosen one:
>>
>> root@vc:/mnt/work/alex/mdadm-neil# ./mdadm --assemble /dev/md200
>> --name=alex --config=none --homehost=vc --run --auto=md --metadata=1.2
>> --verbose --verbose /dev/sdc2 /dev/sdd2
>> mdadm: looking for devices for /dev/md200
>> mdadm: /dev/sdc2 is identified as a member of /dev/md200, slot 0.
>> mdadm: /dev/sdd2 is identified as a member of /dev/md200, slot -1.
>> mdadm: added /dev/sdc2 to /dev/md200 as 0 (possibly out of date)
>> mdadm: no uptodate device for slot 2 of /dev/md200
>> mdadm: added /dev/sdd2 to /dev/md200 as -1
>> mdadm: failed to RUN_ARRAY /dev/md200: Input/output error
>> mdadm: Not enough devices to start the array.
>>
>> Kernel doesn't accept the non-spare drive considering it as non-fresh:
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.679396] md: md200 stopped.
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.686870] md: bind<sdc2>
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.687623] md: bind<sdd2>
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.687675] md: kicking
>> non-fresh sdc2 from array!
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.687680] md: unbind<sdc2>
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.687683] md: export_rdev(sdc2)
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.693574]
>> md/raid1:md200: active with 0 out of 2 mirrors
>> May 27 12:42:28 vsa-00000505-vc-0 kernel: [343203.693583] md200:
>> failed to create bitmap (-5)
>>
>> This happens with the latest mdadm from git, and kernel 3.8.2.
>>
>> Is this the expected behavior?
>
> I hadn't thought about it.
>
>> Maybe mdadm should not consider spares at all for its "chosen_drive"
>> logic, and perhaps not try to add them to the kernel?
>
> Probably not, no.
>
> NeilBrown
>
>
>
>>
>> Superblocks of both drives:
>> sdc2 - the "good" drive:
>> /dev/sdc2:
>> Magic : a92b4efc
>> Version : 1.2
>> Feature Map : 0x1
>> Array UUID : 8e051cc5:c536d16e:72b413fa:e7049d4b
>> Name : zadara_vc:alex
>> Creation Time : Mon May 27 11:33:50 2013
>> Raid Level : raid1
>> Raid Devices : 2
>>
>> Avail Dev Size : 975063127 (464.95 GiB 499.23 GB)
>> Array Size : 209715200 (200.00 GiB 214.75 GB)
>> Used Dev Size : 419430400 (200.00 GiB 214.75 GB)
>> Data Offset : 2048 sectors
>> Super Offset : 8 sectors
>> Unused Space : before=1968 sectors, after=555632727 sectors
>> State : clean
>> Device UUID : 1f661ca3:fdc8b887:8d3638ab:f2cc0a40
>>
>> Internal Bitmap : 8 sectors from superblock
>> Update Time : Mon May 27 11:34:57 2013
>> Checksum : 72a97357 - correct
>> Events : 9
>>
>> sdd2 - the "rebuilding" drive:
>> /dev/sdd2:
>> Magic : a92b4efc
>> Version : 1.2
>> Feature Map : 0x1
>> Array UUID : 8e051cc5:c536d16e:72b413fa:e7049d4b
>> Name : zadara_vc:alex
>> Creation Time : Mon May 27 11:33:50 2013
>> Raid Level : raid1
>> Raid Devices : 2
>>
>> Avail Dev Size : 976123417 (465.45 GiB 499.78 GB)
>> Array Size : 209715200 (200.00 GiB 214.75 GB)
>> Used Dev Size : 419430400 (200.00 GiB 214.75 GB)
>> Data Offset : 2048 sectors
>> Super Offset : 8 sectors
>> Unused Space : before=1968 sectors, after=556693017 sectors
>> State : clean
>> Device UUID : 9abc7fa9:6bf95a51:51f2cd65:14232e81
>>
>> Internal Bitmap : 8 sectors from superblock
>> Update Time : Mon May 27 11:35:56 2013
>> Checksum : 3e793a34 - correct
>> Events : 26
>>
>>
>> Device Role : spare
>> Array State : A. ('A' == active, '.' == missing, 'R' == replacing)
>>
>>
>> Thanks,
>> Alex.
>
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
