1. what kind of disks are these?
HP Hardware Array with default LVM on it. This was just to take live
snapshots of MySQL to be able to restart replication without issue.
2. is /home RAID-5? i'm guessing it is since RAID-10 with 3 drives and
a hot-spare doesn't make any sense. RAID-5 can be dreadfully slow,
especially on random writes.
RAID 5 + hot spare
what kind of virtual disks are you using for the VMś? cow2 image files?
raw or lvm partitions? partitions are much faster than qcow2 files.
Not sure - can't break up the HP array to give it a dedicated disk now
tho. Too much risk of downtime.
3. is /home where users' mail lives?
Yes
or does dovecot move it ~user/Mail or similar from /var/mail?
Do the users use their /home directories for anything else? samba or
nfs exports for example? would you class that as light or heavy usage?
No
iostat -x 10
Linux 2.6.32-573.7.1.el6.x86_64 19/01/16 _x86_64_ (12 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
5.27 0.00 1.74 3.98 0.00 89.01
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz
avgqu-sz await svctm %util
sda 144.40 398.34 92.54 95.71 5790.73 4493.15 54.63
0.32 1.71 1.38 25.92
so you're running a backup at the moment? is that when the slowdown occurs, or
does it happen any old time?
No it was used for a project a couple of years ago and never unplugged
dm-0 0.00 0.00 154.36 81.59 1234.90 652.68 8.00
0.04 0.16 0.44 10.43
dm-1 0.00 0.00 154.36 81.59 1234.90 652.68 8.00
0.04 0.17 0.44 10.44
mysql drives seem fine.
Since its all LVM I guess the "drives" part of it is just the LVM
logical partitions
dm-2 0.00 0.00 0.00 0.00 0.00 0.00 8.00
0.00 3.36 3.07 0.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 8.00
0.00 0.00 0.00 0.00
dm-4 0.00 0.00 9.63 8.24 77.01 65.93 8.00
0.22 12.41 1.52 2.72
dm-5 0.00 0.00 73.20 404.46 4478.78 3774.52 17.28
0.24 0.27 0.46 21.75
it's odd that most of the I/O is on just one of these /home drives.
craig
I guessed that was how the RAID card presented itself to the OS
Cheers
Piers
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