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drive, it will only sync the small parts of the drive that are out of
date, instead of the entire drive.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:

quoted

% 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:

quoted

[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