Re: [Xen-users] Raid1 performance

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Apr 09, 2010 at 11:05:40AM +0200, blub@xxxxxxxx wrote:
> > On Thu, Apr 08, 2010 at 08:23:19PM +0200, blub@xxxxxxxx wrote:
> >> > 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
> >> >
> >> >
> >>
> >> yes, the box has 8 physical cores, and the domU test installation only
> >> uses two of them
> >>
> >
> > How many cores does dom0 have?
> > Did you set up the xen credit scheduler weights?
> > Did you pin the vcpus to specific cores?
> >
> > What does "iostat 1" show in dom0 while you run the test?
> > What does "xm top" show in dom0 while you run test?
> >
> > -- Pasi
> >
> >
> 
> 
> here is the output: http://pastebin.com/c3JqU7e4
> 
> everything looks normal in my opinion
> 

Dom0 should have more weight than the domU!

Was that dstat from domU or from dom0? 

-- Pasi


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users