>> One more glitch? I ran the following command, trying several different
>> locations for the backup file, all of which have plenty of space and
>> are not on the array.
>>
>> sudo mdadm -G /dev/md/0_0 -n 4 --backup-file=/tmp/backmd
>>
>> mdadm gives the message "mdadm: Need to backup 960K of critical
>> section.." and it immediately returns to the command prompt without
>> shrinking the array.
>
> Are you sure its not doing the reshape? Â"cat /proc/mdstat" will show whats happening in the background.
>
> Also, check your dmesg to see if there are any explanatory messages.
>
> Phil
>
I tried again, with the same results. Details follow:
To assemble the array, I used
ubuntu@ubuntu:~/mdadm-3.2$ sudo mdadm --assemble --scan
then
I resynced the array.
then
ubuntu@ubuntu:~/mdadm-3.2$ sudo mdadm --grow /dev/md127 --array-size 5857612608
then
ubuntu@ubuntu:~/mdadm-3.2$ sudo mdadm -G -n 4 --backup-file=mdbak /dev/md127
and again received the messages:
ubuntu@ubuntu:~/mdadm-3.2$ sudo mdadm -G -n 4 --backup-file=mdback /dev/md127
mdadm: Need to backup 960K of critical section..
ubuntu@ubuntu:~/mdadm-3.2$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md127 : active raid5 sda2[0] sdh2[5] sdg2[4] sdf2[3] sde2[2] sdd2[1]
5857612608 blocks level 5, 64k chunk, algorithm 2 [6/6] [UUUUUU]
unused devices: <none>
ubuntu@ubuntu:~/mdadm-3.2$ mdadm -V
mdadm - v3.2 DEVELOPER_ONLY - 1st February 2011 (USE WITH CARE)
The following appear to be the relevant parts of dmesg--
[ 758.516860] md: md127 stopped.
[ 758.522499] md: bind<sdd2>
[ 758.523731] md: bind<sde2>
[ 758.525170] md: bind<sdf2>
[ 758.525588] md: bind<sdg2>
[ 758.526003] md: bind<sdh2>
[ 758.526748] md: bind<sda2>
[ 758.567380] async_tx: api initialized (async)
[ 758.740173] raid6: int64x1 335 MB/s
[ 758.910051] raid6: int64x2 559 MB/s
[ 759.080062] raid6: int64x4 593 MB/s
[ 759.250058] raid6: int64x8 717 MB/s
[ 759.420148] raid6: sse2x1 437 MB/s
[ 759.590013] raid6: sse2x2 599 MB/s
[ 759.760037] raid6: sse2x4 634 MB/s
[ 759.760044] raid6: using algorithm sse2x4 (634 MB/s)
[ 759.793413] md: raid6 personality registered for level 6
[ 759.793423] md: raid5 personality registered for level 5
[ 759.793429] md: raid4 personality registered for level 4
[ 759.798708] md/raid:md127: device sda2 operational as raid disk 0
[ 759.798720] md/raid:md127: device sdh2 operational as raid disk 5
[ 759.798729] md/raid:md127: device sdg2 operational as raid disk 4
[ 759.798739] md/raid:md127: device sdf2 operational as raid disk 3
[ 759.798747] md/raid:md127: device sde2 operational as raid disk 2
[ 759.798756] md/raid:md127: device sdd2 operational as raid disk 1
[ 759.800722] md/raid:md127: allocated 6386kB
[ 759.810239] md/raid:md127: raid level 5 active with 6 out of 6
devices, algorithm 2
[ 759.810249] RAID conf printout:
[ 759.810255] --- level:5 rd:6 wd:6
[ 759.810263] disk 0, o:1, dev:sda2
[ 759.810271] disk 1, o:1, dev:sdd2
[ 759.810278] disk 2, o:1, dev:sde2
[ 759.810285] disk 3, o:1, dev:sdf2
[ 759.810293] disk 4, o:1, dev:sdg2
[ 759.810300] disk 5, o:1, dev:sdh2
[ 759.810416] md127: detected capacity change from 0 to 9996992184320
[ 759.825149] md127: unknown partition table
[ 810.381494] md127: detected capacity change from 9996992184320 to
5998195310592
[ 810.384868] md127: unknown partition table
and here is the information about the array.
sudo mdadm -D /dev/md127
/dev/md127:
Version : 0.90
Creation Time : Thu Jan 6 06:13:08 2011
Raid Level : raid5
Array Size : 5857612608 (5586.25 GiB 5998.20 GB)
Used Dev Size : 1952537536 (1862.08 GiB 1999.40 GB)
Raid Devices : 6
Total Devices : 6
Preferred Minor : 127
Persistence : Superblock is persistent
Update Time : Tue Mar 15 00:45:28 2011
State : clean
Active Devices : 6
Working Devices : 6
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
UUID : 7e946e9d:b6a3395c:b57e8a13:68af0467
Events : 0.76
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
1 8 50 1 active sync /dev/sdd2
2 8 66 2 active sync /dev/sde2
3 8 82 3 active sync /dev/sdf2
4 8 98 4 active sync /dev/sdg2
5 8 114 5 active sync /dev/sdh2
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