Re: mdadm: /dev/md0 has been started with 1 drive (out of 2).

[Adam Goryachev <mailinglists@websitemanagers.com.au>]

Personally, I'd probably do something like:
mdadm --assemble /dev/md0 /dev/sdd1
mdadm --manage /dev/md0 --run
mdadm --manage /dev/md0 --add /dev/sdc1

This will cause a full sync from sdd1 to sdc1, which will then ensure
both copies are identical/up to date.

Personally, I would also do:
mdadm --grow /dev/md0 --bitmap=internal
This means next time you have a similar issue, when you add the older
drive, it will only sync the small parts of the drive that are out of
date, instead of the entire drive.

Note: The above assumes that both drives are fully functional. If you
get a read error on sdd1 during the resync, then you will have
additional problems.

Regards,
Adam

On 05/11/13 19:41, Ivan Lezhnjov IV wrote:
> Hi,
>
> I am new to mdadm/software raid and I've built myself a raid1 array, which after a resume from sleep is assembled with 1 out of 2 devices only.
>
> I queried the web, read some threads on the mailing list and learned that event count on these two devices differe a little, and that in a case like this, it would seem, mdadm --assemble --scan --force is a right action. Tried that, but the array is still assembled with only one device.
>
> Where do I go from here?
>
> --examine output:
>
>> % mdadm --examine /dev/sdc1
>> /dev/sdc1:
>>           Magic : a92b4efc
>>         Version : 1.2
>>     Feature Map : 0x0
>>      Array UUID : c4cf4a52:6daa94c8:6d88a2fa:8f604199
>>            Name : sega:0  (local to host sega)
>>   Creation Time : Fri Nov  1 16:24:18 2013
>>      Raid Level : raid1
>>    Raid Devices : 2
>>
>>  Avail Dev Size : 3906553856 (1862.79 GiB 2000.16 GB)
>>      Array Size : 1953276736 (1862.79 GiB 2000.16 GB)
>>   Used Dev Size : 3906553472 (1862.79 GiB 2000.16 GB)
>>     Data Offset : 262144 sectors
>>    Super Offset : 8 sectors
>>           State : clean
>>     Device UUID : 814f6fb3:a8a93019:c04ef011:cfa16124
>>
>>     Update Time : Tue Nov  5 01:03:48 2013
>>        Checksum : 32aca1de - correct
>>          Events : 22
>>
>>
>>    Device Role : Active device 0
>>    Array State : AA ('A' == active, '.' == missing)
>>
>>
>>
>> % mdadm --examine /dev/sdd1
>> /dev/sdd1:
>>           Magic : a92b4efc
>>         Version : 1.2
>>     Feature Map : 0x0
>>      Array UUID : c4cf4a52:6daa94c8:6d88a2fa:8f604199
>>            Name : sega:0  (local to host sega)
>>   Creation Time : Fri Nov  1 16:24:18 2013
>>      Raid Level : raid1
>>    Raid Devices : 2
>>
>>  Avail Dev Size : 3906553856 (1862.79 GiB 2000.16 GB)
>>      Array Size : 1953276736 (1862.79 GiB 2000.16 GB)
>>   Used Dev Size : 3906553472 (1862.79 GiB 2000.16 GB)
>>     Data Offset : 262144 sectors
>>    Super Offset : 8 sectors
>>           State : clean
>>     Device UUID : cea7f341:435cdefd:5f883265:a75c5080
>>
>>     Update Time : Tue Nov  5 07:53:09 2013
>>        Checksum : 55110136 - correct
>>          Events : 30
>>
>>
>>    Device Role : Active device 1
>>    Array State : .A ('A' == active, '.' == missing)
>
> dmesg output:
>
>> [548246.716474] scsi_verify_blk_ioctl: 18 callbacks suppressed
>> [548246.716484] mdadm: sending ioctl 800c0910 to a partition!
>> [548246.716492] mdadm: sending ioctl 800c0910 to a partition!
>> [548246.716512] mdadm: sending ioctl 1261 to a partition!
>> [548246.716518] mdadm: sending ioctl 1261 to a partition!
>> [548246.718155] mdadm: sending ioctl 800c0910 to a partition!
>> [548246.718163] mdadm: sending ioctl 800c0910 to a partition!
>> [548246.718174] mdadm: sending ioctl 1261 to a partition!
>> [548246.718180] mdadm: sending ioctl 1261 to a partition!
>> [548246.720524] mdadm: sending ioctl 800c0910 to a partition!
>> [548246.720533] mdadm: sending ioctl 800c0910 to a partition!
>> [548247.265498] md: md0 stopped.
>> [548247.269420] md: bind<sdc1>
>> [548247.271426] md: bind<sdd1>
>> [548247.271471] md: kicking non-fresh sdc1 from array!
>> [548247.271478] md: unbind<sdc1>
>> [548247.274669] md: export_rdev(sdc1)
>> [548247.332487] md/raid1:md0: active with 1 out of 2 mirrors
>> [548247.332531] md0: detected capacity change from 0 to 2000155377664
>> [548247.334969]  md0: unknown partition table
>> [548272.306149] md0: detected capacity change from 2000155377664 to 0
>> [548272.306163] md: md0 stopped.
>> [548272.306175] md: unbind<sdd1>
>> [548272.308646] md: export_rdev(sdd1)


-- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au