Re: Help restoring a raid10 Array (4 disk + one spare) after a hard disk failure at power on

[Eric Valette <eric.valette@xxxxxxx>]

On 14/05/2019 19:25, Julien ROBIN wrote:

Thanks a lot. I think I'm ok (rather will be in 5 hours).

> mdadm --assemble /dev/md0 /dev/loop0 /dev/loop1 /dev/loop3 /dev/loop4
> mdadm: /dev/md0 assembled from 3 drives and 1 spare - need all 4 to 
> start it (use --run to insist).

I only did mdadm --assemble --run /dev/md0

and it started rebuilding automatically using the spare. Dunno why it 
did not work automatically (did not put --run the first time I tried).

mdadm --detail /dev/md0
/dev/md0:
           Version : 1.2
     Creation Time : Wed Jun 20 23:56:59 2012
        Raid Level : raid10
        Array Size : 5860268032 (5588.79 GiB 6000.91 GB)
     Used Dev Size : 2930134016 (2794.39 GiB 3000.46 GB)
      Raid Devices : 4
     Total Devices : 4
       Persistence : Superblock is persistent

       Update Time : Tue May 14 19:29:22 2019
             State : clean, degraded, recovering
    Active Devices : 3
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 1

            Layout : near=2
        Chunk Size : 512K

Consistency Policy : resync

    Rebuild Status : 0% complete

              Name : nas2:0  (local to host nas2)
              UUID : 6abe1f20:90c629de:fadd8dc0:ca14c928
            Events : 1194

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync set-A   /dev/sdb1
       1       8       33        1      active sync set-B   /dev/sdc1
       4       8       65        2      spare rebuilding   /dev/sde1
       3       8       49        3      active sync set-B   /dev/sdd1
root@nas2:~# cat /proc/mdstat
Personalities : [raid10]
md0 : active raid10 sdb1[0] sde1[4] sdd1[3] sdc1[1]
      5860268032 blocks super 1.2 512K chunks 2 near-copies [4/3] [UU_U]
      [>....................]  recovery =  0.1% (3835328/2930134016) 
finish=292.4min speed=166753K/sec