[linux-lvm] Performance tunning on LVM2

[Antony MARTINEAU <Antony MARTINEAU lippi fr>]

Hello,
My configuration:
Server DELL 2860 Intel(R) Xeon(R) CPU
 X3230 @ 2.66GHz (Quad Core)
8GB of  memory
2 x SAS 15000 300G0 RAID 0 hardware

SLES 10 SP2
Kernel 2.6.16.60-0.21-xen

i have one volume group vg0 ( whith
one PV, the two disks in raid0) whith many lvm
I am very surprise about LVM2 performance
when a snapshot is done.
Write speed on the Original volume is
very bad when a snaphot is active...

For exemple:

Speed on /dev/vg0/test when there
is NO snapshot :

suse2:~ # dd if=/dev/zero of=/dev/vg0/test
bs=2M count=400
400+0 records in
400+0 records out
838860800 bytes (839 MB) copied, 6.42741
seconds, 131 MB/s

Speed on /dev/vg0/test when there
is one snapshot of this original volume :

suse2:~ # lvremove --force /dev/vg0/test3.snap
  Logical volume "test3.snap"
successfully removed
suse2:~ # dd if=/dev/zero of=/dev/vg0/test
bs=2M count=400
400+0 records in
400+0 records out
838860800 bytes (839 MB) copied, 6.42741
seconds, 131 MB/s
suse2:~ # lvcreate -s -L1G -ntest.snap
/dev/vg0/test
  Logical volume "test.snap"
created
suse2:~ # dd if=/dev/zero of=/dev/vg0/test
bs=2M count=400
400+0 records in
400+0 records out
838860800 bytes (839 MB) copied, 204.862
seconds, 4.1 MB/s


Speed on /dev/vg0/test when there
is 2 snapshots of this original volume :

suse2:~ # lvcreate -s -L1G -ntest1.snap
/dev/vg0/test
  Logical volume "test1.snap"
created
suse2:~ # lvcreate -s -L1G -ntest2.snap
/dev/vg0/test
  Logical volume "test2.snap"
created
suse2:~ # lvremove /dev/vg0/test2.snap
Do you really want to remove active
logical volume "test2.snap"? [y/n]: y
  Logical volume "test2.snap"
successfully removed
suse2:~ # dd if=/dev/zero of=/dev/vg0/test
bs=2M count=400
400+0 records in
400+0 records out
838860800 bytes (839 MB) copied, 270.928
seconds, 3.1 MB/s


Do you know  some elements about
tunning performance?,?

Performances are disastrous
when a snaphot is active
Could you give your speed result? and
your amelioration??

ps:Results are the same whithout Kernel
Xen and whith a kernel more recent (2.6.24.2)

Cordialement,

MARTINEAU Antony Service informatique Assistant informatique LIPPI Management	La Fouillouse 16440 Mouthiers sur Boheme Tel.: 05.45.67.34.35 Courriel: antony martineau lippi fr http://www.lippi.fr

Ce message et toutes les pieces jointes sont etablis a l'attention exclusive
de ses destinataires et sont strictement confidentiels. Pour
en savoir plus cliquer ici

This message and any attachments are confidential to the ordinary user
of the e-mail address to which it was addressed and may also be privileged.
More
information