On Wed, Oct 08, 2008 at 10:51:16AM -0500, Anthony Liguori wrote:
A great deal of virtualization users are doing some form of homogeneous consolidation. If they have a good set of management tools or sophisticated storage, then their guests will be sharing base images or something like that. Caching in the host will result in major performance improvements because otherwise, the same data will be fetched multiple times.
NB, this has no impact on caching of backing files - QEMU masks out the O_DIRECT flag when opening the backing file - so in a shared master image scenario, all reads for the shared file will still be cached, only write5Cs to the cow file are impacted. Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|