What is the recommend way to increase the capacity of a mirror on the
fly?
What seemed obvious to me (remove and then replace each part of the
mirror in turn) doesn't work:
E.g. (for simulation purposes):
Device Boot Start End Blocks Id System
/dev/sdb1 1 33 265041 fd Linux raid autodetect
/dev/sdb2 34 99 530145 fd Linux raid autodetect
Device Boot Start End Blocks Id System
/dev/sdc1 1 33 265041 fd Linux raid autodetect
/dev/sdc2 34 99 530145 fd Linux raid autodetect
$ mdadm --create /dev/md0 --verbose --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdc1
mdadm: array /dev/md0 started.
$ cat /proc/mdstat
Personalities : [raid1]
read_ahead 1024 sectors
md0 : active raid1 sdc1[1] sdb1[0]
264960 blocks [2/2] [UU]
unused devices: <none>
$ mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.00
Creation Time : Wed Jan 22 18:40:33 2003
Raid Level : raid1
Array Size : 264960 (258.75 MiB 271.31 MB)
Device Size : 264960 (258.75 MiB 271.31 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Jan 22 18:40:33 2003
State : dirty, no-errors
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 8 33 1 active sync /dev/sdc1
UUID : 441d90a6:0f20b7cf:0ac9ed56:52bee387
Ok, let's remove sdc1 and replace it with sdc2:
$ mdadm /dev/md0 -f /dev/sdc1 -r /dev/sdc1 -a /dev/sdc2
mdadm: set /dev/sdc1 faulty in /dev/md0
mdadm: hot removed /dev/sdc1
mdadm: hot added /dev/sdc2
But no joy; /dev/sdc2 won't take as mirror:
$ mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.00
Creation Time : Wed Jan 22 18:40:33 2003
Raid Level : raid1
Array Size : 264960 (258.75 MiB 271.31 MB)
Device Size : 264960 (258.75 MiB 271.31 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Jan 22 18:42:13 2003
State : dirty, no-errors
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1
Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 0 0 1 faulty removed
2 8 34 2 /dev/sdc2
UUID : 441d90a6:0f20b7cf:0ac9ed56:52bee387
$ cat /proc/mdstat
Personalities : [raid1]
read_ahead 1024 sectors
md0 : active raid1 sdc2[2] sdb1[0]
264960 blocks [2/1] [U_]
unused devices: <none>
The mirror won't rebuild /dev/sdc2 to match /dev/sdb1.
What do I have to do in order to get /dev/sdc2 to *replace* /dev/sdc1
in the array?
If the answer is "you can't do that", then what is the recommended
method for doing what I'm trying to do?
Thanks,
--
James Ralston, Information Technology
Software Engineering Institute
Carnegie Mellon University, Pittsburgh, PA, USA
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