Re: [Xen-devel] poor I/O performance on domU

[Anthony Liguori <aliguori@xxxxxxxxxx>]

On Sat, 2005-01-15 at 08:36, Jan Kundrát wrote:
> Anthony Liguori wrote:
> yes, dom0 filesystems are on partitions located on hda.

My theory is that since hda is a single disk if you've got dom0 reading
and writing to it and another partition reading and writing to the same
disk at the same time both are going to be slower than if you were just
writing to hda on dom0.

That's why I suggest trying it with a neutral device.

> I've tried exporting /dev/hda7 (not used neither mounted from dom0) as 
> sdb7 and I can get about 12.3 MB/s. From dom0 I get about 14.8 MB/s.

That seems pretty reasonable.  Doesn't seem like there's a problem. 
Sharing partitions between dom0 and domU seems like a bad idea.  Look
through the threads in the list about filesystem corruption.

> Tested by `time dd if=/dev/{s|h}hda7 of=/dev/null bs=1M`, about 4.5GB of 
> data.
> 
> -jkt
-- 
Anthony Liguori
Linux Technology Center (LTC) - IBM Austin
E-mail: aliguori@xxxxxxxxxx
Phone: (512) 838-1208




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