[virt-tools-list] Default use of caching on raw volumes

[Daniel P. Berrange]

On Wed, Aug 18, 2010 at 09:18:37AM -0600, Jamin W. Collins wrote:
> On 08/18/2010 09:06 AM, Daniel P. Berrange wrote:
> >
> >It is not as clearcut as you make it out to be. If cache=none was always
> >the best option,
> 
> Show me a single test case using raw volumes where it's not.  Every test 
> I've done and those of others documented online indicate that disabling 
> caching provides a better performance.  Qemu's own website indicates 
> it'll provide a better performance.

Previously when anyone has suggested setting cache=none for QEMU,
other people have appeared with test results showing that other
cache settings perform better for their workloads. There is no
perfect default setting for everyone. Changing the defaults just
shifts the non-optimal performance problem from one set  people
to a different set of people. If you think QEMU's defaults are
wrong then raise the question of best default cache settings on 
QEMU lists again. Maybe you'll find everyone agrees this time
around, but there hasn't been agreement on previous occassions.

Daniel
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