At Fri, 31 Aug 2012 08:58:22 +0800, Liu Yuan wrote: > > On 08/30/2012 10:42 PM, MORITA Kazutaka wrote: > > I wonder if there is a situation where some users want to enable a > > disk cache of Sheepdog, but the others don't want to. > > The biggest problem is we don't have a sane disk cache implementation for > backend (seems impossible to me). > Current proposed approach doesn't scale. Suppose we have 1000 nodes, and sync > request will be issued in > 30 second. Because we have to broadcast sync request to all the nodes, then > we'll end up with > > 1000^2 / 30 = 33333 > > for every host every second. This will definitely degrade the performance. > That is, O(n^2) will only apply > to very small sized cluster. If we have an O(n) disk cache for backend, then > I think we don't need to disable > it.
Sorry, what I meant is "is there any situation where some qemus want to enable a disk cache of Sheepdog, but the others want to disable it?". Because we are arguing that we need to disable the cache from qemu command line (e.g. with 'cache=none'). I know Hitoshi's patch doesn't scale, but we can disable it with a sheep command line when using many nodes for Sheepdog. -- sheepdog mailing list [email protected] http://lists.wpkg.org/mailman/listinfo/sheepdog
