On Mon, 15 Mar 2010, Sage Weil wrote: > > Snapshots and AIO might be the next things I'll try to implement. Snapshots > > will probably be taken on a per pool basis, since this will make things > > a lot simpler. If you have multiple disk images in one pool, every image > > will be snapshot, but there won't be a reference to the snapshot in the > > metadata of the image. To avoid extra overhead you will have to create a > > new pool for every image. - Ideas for a better solution are welcome. > > There is a better way, but it's a bit more work. As you note the librados > snapshot interface is at a granularity of pools only. The object layer > supports per-object granularity, but it requires a bit of housekeeping on > the part of the client. A 'snap context' can be associated with every > write to tell the OSD what snapids exist and how to do COW. The interface > just isn't exposed via librados. Using it would look something like: > > rados_snapctx_t ctx = ...; > > rados_pool_set_snapctx(pool, ctx); /* use given ctx for writes > via this pool handle */ > rados_alloc_snapid(ctx); /* allocate new snapid, add to ctx */ > /* user is responsible for saving ctx contents somewhere before > using the updated ctx */ > rados_write(pool, ...);
Just to be clear, librados doesn't support this yet, but it should be pretty straightforward to add it. sage ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Ceph-devel mailing list Ceph-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ceph-devel
