[Xen-users] Slow IO in domU

[ÐÑÑÐÐÐ ÐÐÑÐÐÐÐ <ufaweb@xxxxxxxxx>]

Hello.

Tell me please, what could be the cause of very low IO in domU?

In dom0:

root@nas-1:~# mount /dev/nas-1/mogilefs-images /mnt
root@nas-1:~# dd if=/dev/zero of=/mnt/test.file bs=40960 count=100000
100000+0 ÐÐÐÐÑÐÐ ÑÑÐÑÐÐÐ
100000+0 ÐÐÐÐÑÐÐ ÐÐÐÐÑÐÐÐ
 ÑÐÐÐÐÑÐÐÐÐÐ 4096000000 ÐÐÐÑ (4,1 GB), 44,7745 c, 91,5 MB/c
root@nas-1:~# umount /mnt
root@nas-1:~#
root@nas-1:~# grep /dev/nas-1/mogilefs-images
/etc/xen/mogilefs-images.nas-1.lo.ufanet.ru.cfg
                  'phy:/dev/nas-1/mogilefs-images,xvda3,w',
root@nas-1:~# xm create /etc/xen/mogilefs-images.nas-1.lo.ufanet.ru.cfg
Using config file "/etc/xen/mogilefs-images.nas-1.lo.ufanet.ru.cfg".
Started domain mogilefs-images.nas-1.lo.ufanet.ru (id=3)

Let's see that in domU:

root@mogilefs-images:~# mount /dev/xvda3 /mnt
root@mogilefs-images:~# dd if=/dev/zero of=/mnt/test.file bs=40960 count=100000
100000+0 records in
100000+0 records out
4096000000 bytes (4.1 GB) copied, 154.519 s, 26.5 MB/s

Info:

root@nas-1:~# uname -a
Linux nas-1.lo.ufanet.ru 3.2.0-2-amd64 #1 SMP Fri Jun 1 17:49:08 UTC
2012 x86_64 GNU/Linux
root@nas-1:~# xm info
host                   : nas-1.lo.ufanet.ru
release                : 3.2.0-2-amd64
version                : #1 SMP Fri Jun 1 17:49:08 UTC 2012
machine                : x86_64
nr_cpus                : 4
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 3006
hw_caps                :
178bf3ff:efd3fbff:00000000:00001710:00802001:00000000:000037ff:00000000
virt_caps              : hvm
total_memory           : 16383
free_memory            : 14024
free_cpus              : 0
xen_major              : 4
xen_minor              : 1
xen_extra              : .2
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
xen_commandline        : placeholder dom0_mem=2048M
cc_compiler            : gcc version 4.6.3 (Debian 4.6.3-4)
cc_compile_by          : waldi
cc_compile_domain      : debian.org
cc_compile_date        : Sun May  6 18:08:50 UTC 2012
xend_config_format     : 4
root@nas-1:~# xm list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0  2047     4     r-----    220.9
mogilefs-images.nas-1.lo.ufanet.ru           3   128     1     -b----     14.2

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