On Thu, 25 Jul 2013, Gregory Farnum wrote: > On Thu, Jul 25, 2013 at 4:01 PM, Sage Weil <sage@xxxxxxxxxxx> wrote: > > I've added a blueprint for avoiding double-writes when using btrfs: > > > > http://wiki.ceph.com/01Planning/02Blueprints/Emperor/osd:_clone_from_journal_on_btrfs > > > > This should improve throughput significantly when the journal is a file in > > btrfs. > > > > --- > > > > Also, there's one for improving the localized read behavior: > > > > http://wiki.ceph.com/01Planning/02Blueprints/Emperor/librados%2F%2Fobjecter%3A_smarter_localized_reads > > > > For example, for read-only parents of rbd clones, we may as well read from > > the replica in the same host or rack or row--whatever crush can tell > > us--and not the primary. This is good for locality and load distribution > > when certain object sets are hot. > > This blueprint includes work items to set locality information in > libcephfs and via the Hadoop bindings. However, there's still a read > hole issue with read-from-replicas [1] that makes this generally > unwise. Did you consider that when writing this blueprint? > In particular I think we want to discuss if we allow people to use a > more powerful read-from-replica unless we can guarantee their usage of > it is safe (ie, snapshots). Yeah, there's an open bug for that, but the solution doesn't seem interesting enough to warrant a CDS discussion... http://tracker.ceph.com/issues/5388 But if I'm wrong, by all means write one! :) sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
