Hi folks,
I added a fourth drive to a RAID 5 array. After some complications
related to adding a new HD controller at the same time, and thus
changing some device names, I re-created the array and got it working
(in the sense "nothing degraded"). But size results are weird. Each
component partition is 320 G, does anyone have an explanation for the
"Used Dev Size" field value below? The 960 G total size is as it should
be, but in practice Linux reports the array only having 625,019,608
blocks. How can this be, even though the array should be clean with 4
active devices?
$ mdadm -D /dev/md0
/dev/md0:
Version : 01.02.03
Creation Time : Sat Oct 13 01:25:26 2007
Raid Level : raid5
Array Size : 937705344 (894.27 GiB 960.21 GB)
Used Dev Size : 625136896 (298.09 GiB 320.07 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Sat Oct 13 05:11:38 2007
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Name : 0
UUID : 9bf903f8:7fc9eec1:2ff25011:37e9607b
Events : 2
Number Major Minor RaidDevice State
0 253 2 0 active sync
/dev/VolGroup01/LogVol02
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
3 8 17 3 active sync /dev/sdb1
Results for mdadm -E <partition> on all devices appear like this one,
with positions changed:
$ mdadm -E /dev/sdc1
/dev/sdc1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : 9bf903f8:7fc9eec1:2ff25011:37e9607b
Name : 0
Creation Time : Sat Oct 13 01:25:26 2007
Raid Level : raid5
Raid Devices : 4
Used Dev Size : 625137010 (298.09 GiB 320.07 GB)
Array Size : 1875410688 (894.27 GiB 960.21 GB)
Used Size : 625136896 (298.09 GiB 320.07 GB)
Data Offset : 272 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 9b2037fb:231a8ebf:1aaa5577:140795cc
Update Time : Sat Oct 13 10:56:02 2007
Checksum : c729f5a1 - correct
Events : 2
Layout : left-symmetric
Chunk Size : 64K
Array Slot : 1 (0, 1, 2, 3)
Array State : uUuu
Particularly, "Used Dev Size" and "Used Size" report an amount twice the
size of the partition (and device). Array size is here twice the actual
size, even though shown correctly within parentheses.
Finally, mdstat shows the block count as it should be.
$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdb1[3] sdd1[2] sdc1[1] dm-2[0]
937705344 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4]
[UUUU]
unused devices: <none>
Any suggestions on how to fix this, or what to investigate next, would
be appreciated!
--
Marko
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