[pve-devel] multipath problems
dietmar at proxmox.com
Wed Aug 22 07:28:08 CEST 2012
I am just setting up a nexenta storage (community edition) and try to use multipath on the proxmox side:
# multipath -l
mpath1 (3600144f0001e58febc44503399600001) dm-3 NEXENTA,NEXENTASTOR
size=100G features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=-3 status=active
|- 5:0:0:0 sdd 8:48 active undef running
|- 3:0:0:0 sdb 8:16 active undef running
`- 4:0:0:0 sdc 8:32 active undef running
I assume above output is OK so far.
The strange thing is that we get very poor performance. When I test a
single iscsi drive I get:
# hdparm -t /dev/sdc
Timing buffered disk reads: 338 MB in 3.00 seconds = 112.48 MB/sec
root at dell1:~# hdparm -t /dev/sdb
Timing buffered disk reads: 222 MB in 3.01 seconds = 73.69 MB/sec
root at dell1:~# hdparm -t /dev/sdd
Timing buffered disk reads: 262 MB in 3.01 seconds = 87.07 MB/sec
When I test the multipath drive I get:
# hdparm -t /dev/mapper/mpath1
Timing buffered disk reads: 266 MB in 3.02 seconds = 88.04 MB/sec
So there is no speed gain. I already checked that traffic is routed to different network cards.
Any idea why it is that slow?
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