Re: Raid5 reshape

["Nigel J. Terry" <nigel@nigelterry.net>]

Nigel J. Terry wrote:
>
> Neil Brown wrote:
>> On Saturday June 17, nigel@nigelterry.net wrote:
>>  
>>> Any ideas what I should do next? Thanks
>>>
>>>     
>>
>> Looks like you've probably hit a bug.  I'll need a bit more info
>> though.
>>
>> First:
>>
>>  
>>> [root@homepc ~]# cat /proc/mdstat
>>> Personalities : [raid5] [raid4]
>>> md0 : active raid5 sdb1[1] sda1[0] hdc1[4](S) hdb1[2]
>>>       490223104 blocks super 0.91 level 5, 128k chunk, algorithm 2 
>>> [4/3] [UUU_]
>>>       [=>...................]  reshape =  6.9% (17073280/245111552) 
>>> finish=86.3min speed=44003K/sec
>>>
>>> unused devices: <none>
>>>     
>>
>> This really makes it look like the reshape is progressing.  How
>> long after the reboot was this taken?  How long after hdc1 has hot
>> added (roughly)?  What does it show now?
>>
>> What happens if you remove hdc1 again?  Does the reshape keep going?
>>
>> What I would expect to happen in this case is that the array reshapes
>> into a degraded array, then the missing disk is recovered onto hdc1.
>>
>> NeilBrown
>> -
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>>   
> I don't know how long the system was reshaping before the power went 
> off, and then I had to restart when the power came back. It claimed it 
> was going to take 430 minutes, so 6% would be about 25 minutes, which 
> could make good sense, certainly it looked like it was working fine 
> when I went out.
>
> Now nothing is happening, it shows:
>
> [root@homepc ~]# cat /proc/mdstat
> Personalities : [raid5] [raid4]
> md0 : active raid5 sdb1[1] sda1[0] hdc1[4](S) hdb1[2]
>      490223104 blocks super 0.91 level 5, 128k chunk, algorithm 2 
> [4/3] [UUU_]
>      [=>...................]  reshape =  6.9% (17073280/245111552) 
> finish=2281.2min speed=1665K/sec
>
> unused devices: <none>
> [root@homepc ~]#
>
> so the only thing changing is the time till finish.
>
> I'll try removing and adding /dev/hdc1 again. Will it make any 
> difference if the device is mounted or not?
>
> Nigel
Tried remove and add, made no difference:
[root@homepc ~]# mdadm /dev/md0 --remove /dev/hdc1
mdadm: hot removed /dev/hdc1
[root@homepc ~]# cat /proc/mdstat
Personalities : [raid5] [raid4]
md0 : active raid5 sdb1[1] sda1[0] hdb1[2]
      490223104 blocks super 0.91 level 5, 128k chunk, algorithm 2 [4/3] 
[UUU_]
      [=>...................]  reshape =  6.9% (17073280/245111552) 
finish=2321.5min speed=1636K/sec

unused devices: <none>
[root@homepc ~]# mdadm /dev/md0 --add /dev/hdc1
mdadm: re-added /dev/hdc1
[root@homepc ~]# cat /proc/mdstat
Personalities : [raid5] [raid4]
md0 : active raid5 hdc1[4](S) sdb1[1] sda1[0] hdb1[2]
      490223104 blocks super 0.91 level 5, 128k chunk, algorithm 2 [4/3] 
[UUU_]
      [=>...................]  reshape =  6.9% (17073280/245111552) 
finish=2329.3min speed=1630K/sec

unused devices: <none>
[root@homepc ~]#