Hi everyone,
I want to split a large raid1 array (1TB, mounted on /) on my dedicated
server into two smaller arrays (50GB for / and 950GB for /srv).
Therefore I booted into the rescue system and perfomed the following steps:
# md0 was already assembled
$ e2fsck -f /dev/md0
$ resize2fs /dev/md0 40G
$ mdadm --grow /dev/md0 -z 50000000
$ resize2fs /dev/md0
$ mdadm /dev/md0 -f /dev/sda2 -r /dev/sda2
$ cfdisk /dev/sda
In cfdisk I removed the sda2 partition and re-created it with the
smaller size (plus a little bit extra space for metadata).
But if I try to re-add sda2, I get the following error:
$ mdadm -a /dev/md0 /dev/sda2
mdadm: /dev/sda2 reports being an active member for /dev/md0, but a
--re-add fails.
mdadm: not performing --add as that would convert /dev/sda2 in to a spare.
mdadm: To make this a spare, use "mdadm --zero-superblock /dev/sda2" first.
dmesg says:
md: sda2 does not have a valid v1.2 superblock, not importing!
md: md_import_device returned -22
The mdadm version on the rescue system is 3.1.5, but on the actual
system (on which the array probably was created) it is 3.1.4.
I successfully tested these steps on my VM before. After I decreased the
partion size of sda2, re-added it to md0 (wait for re-sync) ... same
with sdb2 ... I booted in my smaller / partiton.
What went wrong here?
Thanks in advance and best regards,
Tobias
Here is some more info (sdb is still untouched):
$ mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sat Feb 9 12:05:33 2013
Raid Level : raid1
Array Size : 50000000 (47.68 GiB 51.20 GB)
Used Dev Size : 50000000 (47.68 GiB 51.20 GB)
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Update Time : Tue Feb 12 10:53:47 2013
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Name : 1350:0
UUID : c7ce3900:ac8a1438:a7e72dbb:16708643
Events : 83
Number Major Minor RaidDevice State
0 0 0 0 removed
1 8 18 1 active sync /dev/sdb2
$ blockdev --getsz /dev/sda /dev/sdb /dev/sda2 /dev/sdb2
1953525168
1953525168
117194175
1940668065
$ mdadm --examine /dev/sd[ab]2
/dev/sda2:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : c7ce3900:ac8a1438:a7e72dbb:16708643
Name : 1350:0
Creation Time : Sat Feb 9 12:05:33 2013
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 1940666017 (925.38 GiB 993.62 GB)
Array Size : 100000000 (47.68 GiB 51.20 GB)
Used Dev Size : 100000000 (47.68 GiB 51.20 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 1138ef85:f279a537:c358a4ac:1ed3949d
Update Time : Tue Feb 12 09:13:10 2013
Checksum : 3345a566 - correct
Events : 69
Device Role : Active device 0
Array State : AA ('A' == active, '.' == missing)
/dev/sdb2:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : c7ce3900:ac8a1438:a7e72dbb:16708643
Name : 1350:0
Creation Time : Sat Feb 9 12:05:33 2013
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 1940666017 (925.38 GiB 993.62 GB)
Array Size : 100000000 (47.68 GiB 51.20 GB)
Used Dev Size : 100000000 (47.68 GiB 51.20 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 6953a768:f643948d:7df649d7:3dfb69c9
Update Time : Tue Feb 12 11:05:54 2013
Checksum : c2686b16 - correct
Events : 85
Device Role : Active device 1
Array State : .A ('A' == active, '.' == missing)
$ fdisk -l /dev/sd[ab]
Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x34e04fde
Device Boot Start End Blocks Id System
/dev/sda1 128520 12851999 6361740 82 Linux swap / Solaris
/dev/sda2 * 12852000 114414929 50781465 fd Linux raid
autodetect
Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x72b56b83
Device Boot Start End Blocks Id System
/dev/sdb1 128520 12851999 6361740 82 Linux swap / Solaris
/dev/sdb2 * 12852000 1953520064 970334032+ fd Linux raid
autodetect
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