LVM thin on raid5 always busy

Aleksej

Well-Known Member
Feb 25, 2018
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Hello.
I've created thin pool from lvm raid5 like this

Code:
pvcreate /dev/sd[a-c]
vgcreate myvg /dev/sda /dev/sdb /dev/sdc
lvcreate -n mylv -L 700G -i 2 --type raid5 myvg
lvcreate -n mymetalv -L 15G -i 2 --type raid5 myvg
lvconvert --thinpool myvg/mylv -poolmetadata myvg/mymetalv

All fine.
I moved 1 VM to it with clean windows install.
VM is very slow. Task manager shows disk usage 100%, react 60-7000ms, but read write about 30-80Kb/s

On host nmon shows always read aprox 40Mb/s and write aprox 15Mb/s.

Code:
DiskName Busy    Read    Write       Xfers   Size  Peak%  Peak=R+W    InFlight
dm-14     91%  33083.0  11994.9KB/s 11262.2  4.0KB  373%  210130.6KB/s 824
dm-16     32%  38975.1  12646.5KB/s 12889.9  4.0KB  165%  210107.6KB/s  04
dm-18     39%  32837.0  12964.3KB/s 11389.0  4.0KB  163%  210075.6KB/s 964
sda       79%  36868.2  11445.6KB/s  253.4 190.7KB  374%  210140.5KB/s  8
sdb       41%  30489.3  10502.0KB/s  216.4 189.4KB  169%  210052.6KB/s  0
sdc       49%  46243.7  13690.3KB/s  310.9 192.8KB  164%  210084.6KB/s  1

What can it be?
 
Hello.
I've created thin pool from lvm raid5 like this

Code:
pvcreate /dev/sd[a-c]
vgcreate myvg /dev/sda /dev/sdb /dev/sdc
lvcreate -n mylv -L 700G -i 2 --type raid5 myvg
lvcreate -n mymetalv -L 15G -i 2 --type raid5 myvg
lvconvert --thinpool myvg/mylv -poolmetadata myvg/mymetalv

All fine.
I moved 1 VM to it with clean windows install.
VM is very slow. Task manager shows disk usage 100%, react 60-7000ms, but read write about 30-80Kb/s

On host nmon shows always read aprox 40Mb/s and write aprox 15Mb/s.

Code:
DiskName Busy    Read    Write       Xfers   Size  Peak%  Peak=R+W    InFlight
dm-14     91%  33083.0  11994.9KB/s 11262.2  4.0KB  373%  210130.6KB/s 824
dm-16     32%  38975.1  12646.5KB/s 12889.9  4.0KB  165%  210107.6KB/s  04
dm-18     39%  32837.0  12964.3KB/s 11389.0  4.0KB  163%  210075.6KB/s 964
sda       79%  36868.2  11445.6KB/s  253.4 190.7KB  374%  210140.5KB/s  8
sdb       41%  30489.3  10502.0KB/s  216.4 189.4KB  169%  210052.6KB/s  0
sdc       49%  46243.7  13690.3KB/s  310.9 192.8KB  164%  210084.6KB/s  1

What can it be?

Actually, i found this information (about thin pool with raid5) on this forum.
But i haven't noticed, that lvconvert on raid levels starts resync.

In this case stable disk load caused by resync, that is visible by lvs -a.