Hello all.
I recently updated an Ubuntu 12.04 LTS system to a 14.04 LTS system.
This upgrade did not go particularly smoothly, and I've been dealing
with various types of weirdness ever since.
This system has 4 hard drives in it, comprising 3 RAID 1 arrays. One
pair of drives contains two arrays - one for / (md0), and one for
/home (md2). The other array is a pair of older drives (the original
array from when the machine was first built) which I have mounted as
/home/backups (md3)
Some investigation has me thinking that perhaps the arrays had gotten
out of sync, or perhaps there was even a failing drive. So I've been
checking and repairing arrays to see what happens.
All drives passed their long SMART tests with no issues.
Even after multiple checks, repairs, and rebuilds, the arrays on the
bigger drives (/ and /home) are showing insanely high mismatch_cnt
values. This has me concerned.
Here are the details:
$cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5]
[raid4] [raid10]
md3 : active raid1 sdb4[3] sda4[2]
660213568 blocks super 1.2 [2/2] [UU]
md0 : active raid1 sda2[2] sdb2[3]
307068736 blocks super 1.2 [2/2] [UU]
md2 : active raid1 sdc1[0] sdd1[1]
2930133824 blocks super 1.2 [2/2] [UU]
unused devices: <none>
$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun Jun 9 19:19:32 2013
Raid Level : raid1
Array Size : 307068736 (292.84 GiB 314.44 GB)
Used Dev Size : 307068736 (292.84 GiB 314.44 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Sat Oct 4 10:18:58 2014
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Name : karzai:0 (local to host karzai)
UUID : ff878502:6d567c41:4dbd32f7:7a1122be
Events : 256772
$ sudo mdadm -D /dev/md2
/dev/md2:
Version : 1.2
Creation Time : Sat Jun 8 04:09:23 2013
Raid Level : raid1
Array Size : 2930133824 (2794.39 GiB 3000.46 GB)
Used Dev Size : 2930133824 (2794.39 GiB 3000.46 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Sat Oct 4 10:19:33 2014
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Name : karzai:2 (local to host karzai)
UUID : dd5af8bf:02a9500e:0b73f986:72a2ba43
Events : 459
Number Major Minor RaidDevice State
0 8 33 0 active sync /dev/sdc1
1 8 49 1 active sync /dev/sdd1
Number Major Minor RaidDevice State
3 8 18 0 active sync /dev/sdb2
2 8 2 1 active sync /dev/sda2
$ sudo mdadm -D /dev/md3
/dev/md3:
Version : 1.2
Creation Time : Sun Jun 9 20:05:28 2013
Raid Level : raid1
Array Size : 660213568 (629.63 GiB 676.06 GB)
Used Dev Size : 660213568 (629.63 GiB 676.06 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Sat Oct 4 09:52:47 2014
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Name : karzai:3 (local to host karzai)
UUID : e60332c8:e5568487:df2f3b61:94fd2b2c
Events : 14971
Number Major Minor RaidDevice State
3 8 20 0 active sync /dev/sdb4
2 8 4 1 active sync /dev/sda4
$ grep . /sys/block/md?/md/mismatch_cnt
/sys/block/md0/md/mismatch_cnt:3148032
/sys/block/md2/md/mismatch_cnt:20217856
/sys/block/md3/md/mismatch_cnt:0
fsck of md2 and md3 were clean
Should I be concerned? The fact that the high counts on on arrays that
share the same physical drives has me very nervous, notwithstanding
the passed SMART tests.
Thank you.
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