Re: Stuck reshape

[NeilBrown <neilb@suse.de>]

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On Fri, 22 Nov 2013 13:17:52 -0600 Larkin Lowrey <llowrey@nuclearwinter.com>
wrote:

> I have a reshape that got stuck on what appears to be step 1 of the process.
> 
> What can be done? Will a shutdown be recoverable, or should I be
> prepared to restore from backup?
> 
> I can read from the array w/o error.

If it is convenient to take a backup, or a copy of the more important files,
that might not be a bad idea.  It shouldn't be necessary, but better safe
than sorry.

> 
> I initiated the re-shape with the following command (devices 4->5, level
> 5->6, chunk 512->256):
> mdadm --grow /dev/md1 --level=6 --raid-devices=6 --chunk=256

So devices: 4 -> 6 ??

> 
> The output was:
> mdadm: level of /dev/md1 changed to raid6
> mdadm: Need to backup 3072K of critical section..
> 
> The status is:
> 
> md1 : active raid6 sdo1[6] sdn1[5] sdd1[2] sdb1[4] sdc1[0] sda1[1]
>       2929890816 blocks super 1.2 level 6, 512k chunk, algorithm 18
> [6/5] [UUUU_U]
>       [>....................]  reshape =  0.0% (512/976630272)
> finish=56199369.9min speed=0K/sec
>       bitmap: 0/1 pages [0KB], 1048576KB chunk
> 
> This process is chewing up a lot of CPU:
>  2858 root      20   0    7936   3692    280 R  91.5  0.0  35:23.72 mdadm
>  2856 root      20   0       0      0      0 R  24.4  0.0  14:05.14
> md1_raid6
>  2857 root      20   0       0      0      0 R  12.2  0.0   4:28.68
> md1_reshape
> 
> (that's 91.5% for mdadm, 24.4% for md1_raid6, and 12.2% for md1_reshape)
> 
> All drives are on-line and functioning normally. I did forget to remove
> the internal bitmap and I also forgot to use an external backup file.

You don't need a backup file when increasing the number of data drives, and
recent kernels don't need you to remove the bitmap (and one those that did,
it would fail cleanly).
So these aren't problems.

Still, something is clearly wrong.

It should be completely safe to reboot ... but given that I don't know what
the reshape is hanging here I cannot promise that the reshape won't hang
again after a reboot.

I'll try to reproduce this and see if I can understand what is happening.
Meanwhile ... maybe try killing mdadm.  That certainly won't hurt and may
help.

NeilBrown

> 
> mdadm - v3.2.6 - 25th October 2012
> kernel: 3.11.8-200.fc19.x86_64
> 
> Syslog is:
> 
> [  601.373480] md: bind<sdn1>
> [  601.773482] md: bind<sdo1>
> [  601.824051] RAID conf printout:
> [  601.824058]  --- level:5 rd:4 wd:4
> [  601.824062]  disk 0, o:1, dev:sdc1
> [  601.824065]  disk 1, o:1, dev:sda1
> [  601.824068]  disk 2, o:1, dev:sdd1
> [  601.824071]  disk 3, o:1, dev:sdb1
> [  601.824073] RAID conf printout:
> [  601.824075]  --- level:5 rd:4 wd:4
> [  601.824078]  disk 0, o:1, dev:sdc1
> [  601.824080]  disk 1, o:1, dev:sda1
> [  601.824083]  disk 2, o:1, dev:sdd1
> [  601.824085]  disk 3, o:1, dev:sdb1
> [  647.692320] md/raid:md1: device sdd1 operational as raid disk 2
> [  647.698547] md/raid:md1: device sdb1 operational as raid disk 3
> [  647.704787] md/raid:md1: device sdc1 operational as raid disk 0
> [  647.710941] md/raid:md1: device sda1 operational as raid disk 1
> [  647.718258] md/raid:md1: allocated 5394kB
> [  647.752152] md/raid:md1: raid level 6 active with 4 out of 5 devices,
> algorithm 18
> [  647.760088] RAID conf printout:
> [  647.760092]  --- level:6 rd:5 wd:4
> [  647.760096]  disk 0, o:1, dev:sdc1
> [  647.760100]  disk 1, o:1, dev:sda1
> [  647.760103]  disk 2, o:1, dev:sdd1
> [  647.760105]  disk 3, o:1, dev:sdb1
> [  648.622041] RAID conf printout:
> [  648.622049]  --- level:6 rd:6 wd:5
> [  648.622053]  disk 0, o:1, dev:sdc1
> [  648.622057]  disk 1, o:1, dev:sda1
> [  648.622059]  disk 2, o:1, dev:sdd1
> [  648.622062]  disk 3, o:1, dev:sdb1
> [  648.622065]  disk 4, o:1, dev:sdo1
> [  648.622072] RAID conf printout:
> [  648.622074]  --- level:6 rd:6 wd:5
> [  648.622077]  disk 0, o:1, dev:sdc1
> [  648.622079]  disk 1, o:1, dev:sda1
> [  648.622082]  disk 2, o:1, dev:sdd1
> [  648.622084]  disk 3, o:1, dev:sdb1
> [  648.622087]  disk 4, o:1, dev:sdo1
> [  648.622089]  disk 5, o:1, dev:sdn1
> [  648.622475] md: reshape of RAID array md1
> [  648.626832] md: minimum _guaranteed_  speed: 1000 KB/sec/disk.
> [  648.633041] md: using maximum available idle IO bandwidth (but not
> more than 200000 KB/sec) for reshape.
> [  648.643053] md: using 128k window, over a total of 976630272k.
> 
> --Larkin
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