> Can you elaborate on that? I don't think there needs to be a difference. Ceph > is hosting mostly filesystems, so it's all just a bunch of filesystem > transactions anyway... >
There is some additional background information here [1]. The XFS journal protects "atomic" (for lack of a better word) actions that actually require multiple disk writes in implementation. The Ceph journal acts similarly to ensure that Ceph-level "atomic" actions can be consistently applied to the underlying filesystem in case of failure (e.g. if ceph-osd crashed in the middle of one of these compound "atomic" Ceph metadata updates -- XFS wouldn't know how to get the system back to a consistent state). As Ilya alluded to, the forthcoming NewStore is able to avoid costly double-writes in certain scenarios such as create, append and overwrite operations by decoupling objects from the underlying filesystem's actual storage path. [1] https://github.com/ceph/ceph/blob/master/doc/rados/configuration/journal-ref.rst -- Jason Dillaman _______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
