I have an array that failed to readd a member saying that the new
member was too small. After trying a few things including "--add",
"--force", zeroing out the superblock, clearing out the first 100 MB
to get rid of the partition table, I found that mdadm thinks the Used
Dev Size is unknown. I looked at the superblock and it appears to have
a valid used dev size. Both disks are exactly the same size. I'm not
sure how fix this.
# mdadm --version
mdadm - v3.3.2 - 21st August 2014
# mdadm --detail /dev/md_root
/dev/md_root:
Version : 1.0
Creation Time : Wed Sep 7 15:58:30 2016
Raid Level : raid1
Array Size : 5368708928 (5120.00 GiB 5497.56 GB)
Used Dev Size : unknown
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Dec 19 17:05:29 2016
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Name : 10.91.0.11-volume
UUID : 2ea91e32:59b7806d:956803c6:00c410eb
Events : 3691225
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
2 0 0 2 removed
# mdadm --detail /dev/md_root
/dev/md_root:
Version : 1.0
Creation Time : Wed Sep 7 15:58:30 2016
Raid Level : raid1
Array Size : 5368708928 (5120.00 GiB 5497.56 GB)
Used Dev Size : unknown
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Dec 19 17:05:29 2016
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Name : 10.91.0.11-volume
UUID : 2ea91e32:59b7806d:956803c6:00c410eb
Events : 3691225
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
2 0 0 2 removed
# hexdump -C -s 5497558130688 /dev/sdb
4ffffffe000 fc 4e 2b a9 01 00 00 00 01 00 00 00 00 00 00 00
|.N+.............|
4ffffffe010 2e a9 1e 32 59 b7 80 6d 95 68 03 c6 00 c4 10 eb
|...2Y..m.h......|
4ffffffe020 31 30 2e 39 31 2e 30 2e 31 31 2d 76 6f 6c 75 6d
|10.91.0.11-volum|
4ffffffe030 65 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
|e...............|
4ffffffe040 86 8d d0 57 00 00 00 00 01 00 00 00 00 00 00 00
|...W............|
4ffffffe050 80 fe ff 7f 02 00 00 00 00 00 00 00 02 00 00 00
|................|
4ffffffe060 a0 ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00
|................|
4ffffffe070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
|................|
4ffffffe080 00 00 00 00 00 00 00 00 e8 fe ff 7f 02 00 00 00
|................|
4ffffffe090 f0 ff ff 7f 02 00 00 00 00 00 00 00 00 00 00 00
|................|
4ffffffe0a0 00 00 00 00 00 00 00 00 4c 6c 99 5a bd 1a 4c 7d
|........Ll.Z..L}|
4ffffffe0b0 32 29 7a bc e2 45 89 dd 00 00 08 00 f8 ff ff ff
|2)z..E..........|
4ffffffe0c0 4f 66 58 58 00 00 00 00 7b 33 38 00 00 00 00 00
|OfXX....{38.....|
4ffffffe0d0 ff ff ff ff ff ff ff ff 33 f3 f0 e6 80 00 00 00
|........3.......|
4ffffffe0e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
|................|
*
4ffffffe100 00 00 fe ff fe ff fe ff fe ff fe ff fe ff fe ff
|................|
4ffffffe110 fe ff fe ff fe ff fe ff fe ff fe ff fe ff fe ff
|................|
*
4ffffffe200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
|................|
*
50000000000
# blockdev --report /dev/sd[a,b]
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 0 5497558138880 /dev/sda
rw 256 512 4096 0 5497558138880 /dev/sdb
# mdadm /dev/md_root --add /dev/sda
mdadm: /dev/sda not large enough to join array
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
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