Re: [Xen-users] Poor disk io performance in domUs

[Andrej Radonic <rado@xxxxxxxxxxxxx>]

Tom,

> Are the disk I/O numbers quoted below aggregate for all machines, or  
> just for the mailserver.
so far we measured separately in dom0 and in the mail-domU.
The 20 MB/s happen as soon as there is concurrent io from two or more domUs.

Andrej

> -- -- Tom Mornini, CTO -- Engine Yard, Ruby on Rails Hosting -- Support, 
> Scalability, Reliability -- (866) 518-YARD (9273) On Jun 20, 2007, at 10:49 PM, 
> Andrej Radonic wrote:
> > > Hi,
> > >
> > > in a previously well behaving xen setup we are suddenly  
> > > experiencing massive loss of disk performance.
> > >
> > > Setup: two identical machines (dell, 2 quadcore cpus each, 8 GB RAM  
> > > each), attached to *one* SAS storagebox (Raid5 SAS disks), CentOS  
> > > 5, Xen 3.04 running three domUs each.
> > > Storage partitions are exposed as block-devices to the guests.  
> > > Filesystem is ext3.
> > >
> > > Since a domU running a rather heavily loaded mailserver (many small  
> > > files, many reads/writes) has been added, io performance has  
> > > deteriorated significantly.
> > >
> > > In dom0 about 100 MB/s can be achieved, in domU only about 50 MB/s.  
> > > This looks even worse when there are massive concurrent / parallel  
> > > io jobs, then throughput goes down to 20 MB/s.
> > >
> > > During all this the cpus are mostly idle...
> > >
> > > Any ideas? I know some performance degradation is to be expected  
> > > but shurely not on this scale?
> > > Thanks,
> > > Andrej
> > >
> > >
> > > _______________________________________________
> > > Xen-users mailing list
> > > Xen-users@xxxxxxxxxxxxxxxxxxx
> > > http://lists.xensource.com/xen-users


interSales AG Internet Commerce
Andrej Radonic
Vorstand

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