Re: [Xen-users] Disk IO trouble in Xen

[Sadique Puthen <sputhenp@xxxxxxxxxx>]

Are you using a pre-allocated image or a sparse file? If the latter it's 
likely to have performance problems like you found?  What if you test 
with dd or iozone or bonnie++?
--Sadique

Greg Hellings wrote:
> 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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>
>   

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