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[Xen-users] Xen4.0.1 : slow Disk IO on DomU

To: Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Xen4.0.1 : slow Disk IO on DomU
From: Erwan RENIER <erwan.renier@xxxxxxxxxxx>
Date: Wed, 16 Mar 2011 23:31:31 +0100
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Hi,
When i test the IO bandwidth it's pretty much slower on DomU :

Dom0 read  : 180MB/s write  : 60MB/s
DomU read  : 40MB/s write :  6MB/s

The main storage is a soft raid5 array of 5 sata2 disk 7200rpm
I tested with a physical partition on one disk and it'about the same ( without raid and without lvm )

DomU disks are Dom0 logical volumes, i use paravirtualized guests, the fs type is ext4.

I already tried the ext4 options barrier=0,data=writeback , it doesn't realy change anything.
I tried too with ext2 and ext3 , it's the same.

Is this normal ?
If not what do you think the problem is?
Thanks.


dist : debian sqeeze
xen : Xen 4.0.1
kernel Dom0 & DomU : 2.6.32-5-xen-amd64
FS : ext4


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