Michal Privoznik <mprivozn@xxxxxxxxxx> : > > On 7/29/19 3:51 AM, Ming-Hung Tsai wrote: > > I'm curious that why librbd sets this limitation? The rule first > > appeared in librbd.git commit d57485f73ab. Theoretically, a > > write-through cache is also safe for VM migration, if the cache > > implementation guarantees that cache invalidation and disk write are > > synchronous operations. > > > > For example, I'm using Ceph RBD images as VM storage backend. The Ceph > > librbd supports synchronous write-through cache, by setting > > rbd_cache_max_dirty to zero, and setting > > rbd_cache_block_writes_upfront to true, thus it would be safe for VM > > migration. Is that true? Any suggestion would be appreciated. Thanks. > > The commit you refer to is very old and my hunch is that things looked > different in 2012. Things might have changed since then and if > write-through wasn't safe ~7 years ago, it might be safe now (with some > tuning). > > Michal Yes, but now the limitation is still there, in qemuMigrationSrcIsSafe(). Should we relax the limitation? Ming-Hung Tsai _______________________________________________ libvirt-users mailing list libvirt-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvirt-users
