Re: [Qemu-devel] [PATCH] QEMU: change default disk cache behavior

[Anthony Liguori <anthony@codemonkey.ws>]

On 05/20/2010 04:32 AM, Jes.Sorensen@redhat.com wrote:
> From: Jes Sorensen<Jes.Sorensen@redhat.com>
>
> We seem to get into the discussion of what is the correct default
> setting disk images in QEMU. The libvirt team is reluctant to change
> specified for newly created images without the default setting
> matching it, and everybody seems to agree that the current setting of
> WT is the worse possible option.
>
> 'nocache' seems to be the preferred option, but it doesn't work for
> all cases, like images on ramfs, NFS etc.
>
> Therefore, here is a patch that does two things:
>   - default to "nocache"
>   - in case of failure with nocache, retry with "write-back"
>    

This sort of change requires performance data in a variety of 
circumstances to justify.

And I strongly suspect that such a blanket change would be wrong but 
that a more targeted change like making cache=none default for physical 
devices would satisfy mostly everyone.

Regards,

Anthony Liguori

> Jes Sorensen (1):
>    QEMU: Change default disk caching to nocache
>
>   vl.c |   25 +++++++++++++++++++------
>   1 files changed, 19 insertions(+), 6 deletions(-)
>
>
>