Re: [Xen-users] Raid1 performance

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Apr 08, 2010 at 07:00:11PM +0200, blub@xxxxxxxx wrote:
> hello
> i've been trying to achieve reasonable disk i/o performance on xen.
> on debian 5.0.4 (xen 3.2.1, kernel 2.6.26) the pv/hvm performance is
> alright with a raid1 inside the domU. unfortunately the qemu version
> (0.9.0) does not cover my needs.
> 
> so i've been trying xen 3.4.2 & 4.0.0rc8 on gentoo (2.6.31)
> on both versions, the disk i/o performance drops to zero when copying
> large files. initially the performance is ok (~30mbyte/s) but drops to
> zero after ~300mb, i've tried it with wget/ftp/scp
> this happens with both PV & HVM domU's. i've tried multiple nic drivers
> 
> the performance seems alright if no raid1 is running on the domU
> i cannot run the domU raid1's on the dom0 since there are multiple dom0s
> connecting to multiple FC SAN's and the raid1's are done across the SAN's
> 
> (btw, the performance with raid1's on the SAN's is excellent on dom0)
> 
> anyone else has experienced this issue?
> 

Did you make sure dom0 has more weight than the domUs, so that it is able
to process the IO requests? 

See: http://wiki.xensource.com/xenwiki/XenBestPractices

-- Pasi


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