[Xen-users] Disk IO trouble in Xen

[Greg Hellings <greg.hellings@xxxxxxxxxxxx>]

I'm having terrible IO trouble with an image based domu


This is the performance on the Dom0
[root@localhost /]# hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   3228 MB in  2.00 seconds = 1617.22 MB/sec
 Timing buffered disk reads:  174 MB in  3.02 seconds =  57.60 MB/sec


And this is the performance on the DomU
[root@localhost ~]# hdparm -tT /dev/xvda

/dev/xvda:
 Timing cached reads:   3336 MB in  2.00 seconds = 1669.98 MB/sec
 Timing buffered disk reads:   26 MB in  3.13 seconds =   8.30 MB/sec


Is it normal for the performance difference to be so great?  I'm running
CentOS 5 and the DomU image is stored on a LVM ReiserFS formatted partition.

Here is the config for the DomU
name = "dddevdb"
uuid = "927f1e915813c2dec60c8f76c2716783"
maxmem = 3072
memory = 2042
vcpus = 2
bootloader = "/usr/bin/pygrub"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
vfb = [ "type=vnc,vncunused=1,keymap=en-us" ]
disk = [ "tap:aio:/var/lib/xen/images/dddevdb.img,xvda,w"]
vif = [ "mac=00:16:3e:62:7a:d1,bridge=xenbr0" ]


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