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

[Tom Mornini <tmornini@xxxxxxxxxxxxxx>]

Are the disk I/O numbers quoted below aggregate for all machines, or  
just for the mailserver.
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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
>
>
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