I’m having difficulty shrinking down a RAID6 array (md2) on a Sinology NAS. I wish to go from 13 drives to 11, and believe I need to go to 12 first to maintain operation and redundancy through the resizing process.
The -array-size has already been shrunk to account for the two drives I wish to remove, and one of the devices has been removed and the machine restarted before the command output below was generated.
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# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md2 : active raid6 sda3[0] sdia3[14] sdib3[9] sdic3[10] sdid3[11] sdie3[12] sdg3[17] sdf3[5] sde3[16] sdd3[3] sdc3[13] sdb3[15]
26329895935 blocks super 1.2 level 6, 64k chunk, algorithm 2 [13/12] [UUUUUUU_UUUUU]
md1 : active raid1 sda2[0] sdb2[1] sdc2[2] sdd2[3] sde2[4] sdf2[5] sdg2[6]
2097088 blocks [8/7] [UUUUUUU_]
md0 : active raid1 sda1[0] sdb1[1] sdc1[2] sdd1[3] sde1[4] sdf1[5] sdg1[6]
2490176 blocks [8/7] [UUUUUUU_]
unused devices: <none>
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When running
# mdadm --grow -n 12 /dev/md2 --backup-file=/mnt/backup-file3
mdadm: max_devs [384] of [/dev/md2]
mdadm: Need to backup 7040K of critical section..
mdadm: Cannot set device shape for /dev/md2: Invalid argument
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dmesg just reports:
[87908.606245] md: couldn't update array info. -22
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# uname -a
Linux diskstation 3.10.77 #7135 SMP Thu Oct 15 13:36:56 CST 2015 x86_64 GNU/Linux synology_avoton_1815+
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Anyone have advice on how to proceed? I thought shrinking of a RAID6 array is supported as long as you use a backup file to allow recovery of the initial blocks
-DW
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