Re: Install failes after md raid replace

[Tobias Lang]

Am 04.01.16 um 17:51 schrieb Andrei Borzenkov:
> 04.01.2016 12:40, Tobias Lang пишет:
>> Hi everybody,
>>
>> after the replacement of a faulty disk in a md raid setup (Raid 1), we
>> are not able to update grub.
>>
>> The system is an Ubuntu 12.04.5 LTS, with the latests patches installed,
>> and running Linux version 3.2.0-95-generic (address@hidden).
>>
>> Disk replacement procedure involved the following steps:
>>
>> # sgdisk -R /dev/sda /dev/sdb
>> # sgdisk -G /dev/sda
>> # mdadm /dev/mdX -a /dev/sdbX
>>
> 
> Sorry, I do not understand this. I assume /dev/sdb is the current good
> disk and /dev/sda is replacement disk. In this case you are trying to
> add disk that already exists in array once more. This is simply not
> possible.

The disk showed a failure like this:

----------------------------------------------------
md2 : active raid1 sdb3[1] sda3[0](F)
      1073740664 blocks super 1.2 [2/1] [_U]
----------------------------------------------------

I removed the disk from the array before replacing it with a new one:

# mdadm /dev/mdX -r /dev/sdaX

After that, the array only had one disk (as this is a two disk array).

>> After resync, this failes:
>>
> 
> Resync? I get "/dev/vdb1 busy".

Of course, the raid has to resync the data to the replaced (and
currently) empty disk.

> Please show exact steps to reproduce starting with degraded array; and
> show array state at each step (cat /proc/mdstat and mdadm --detail
> /dev/mdX).
> 

The current /proc/mdstat looks like this:

----------------------------------------------------
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md1 : active raid1 sda2[2] sdb2[1]
      524276 blocks super 1.2 [2/2] [UU]

md3 : active raid1 sda4[2] sdb4[1]
      1822442815 blocks super 1.2 [2/2] [UU]

md2 : active raid1 sda3[2] sdb3[1]
      1073740664 blocks super 1.2 [2/2] [UU]

md0 : active raid1 sda1[2] sdb1[1]
      33553336 blocks super 1.2 [2/2] [UU]

unused devices: <none>

----------------------------------------------------

An example 'mdadm --detail /dev/md0' looks like this:

----------------------------------------------------
/dev/md0:
        Version : 1.2
  Creation Time : Fri Apr 19 10:11:20 2013
     Raid Level : raid1
     Array Size : 33553336 (32.00 GiB 34.36 GB)
  Used Dev Size : 33553336 (32.00 GiB 34.36 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Sat Jan  2 22:25:50 2016
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : rescue:0
           UUID : 72974d0d:40970c9e:83dfc291:dd07bfba
         Events : 162

    Number   Major   Minor   RaidDevice State
       2       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1

----------------------------------------------------

Best regards

Tobi

-- 
Dr. Tobias Lang
TrevoTrend GmbH
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