Am 09.01.2013 11:36, schrieb Liu Yuan: > On 01/09/2013 06:25 PM, Paolo Bonzini wrote: >> But why is it useful to force-disable writeback caching? Do you have >> any performance numbers? > > This is not related to performance. What I want is to allow users to > choose Sheepdog cache mode (writethrough/writeback/directio) from cache=xxx.
The question was which effects these modes have, and especially what the user-visible differences between writeback+flush and writethrough cache are. > Obviously writeback mode show much better write performance over > writethrough cache in Sheepdog. NOTE: writethrough cache in Sheepdog is > a readonly cache which is always consistent with cluster data thus need > no flush at all. This is to boost read performance for read intensive > Guest over Sheepdog iamges. This is the definition of a writethrough cache. Kevin
