On Sat, 7 Sep 2013, Oliver Daudey wrote: > Hey all, > > This topic has been partly discussed here: > http://lists.ceph.com/pipermail/ceph-users-ceph.com/2013-March/000799.html > > Tested on Ceph version 0.67.2. > > If you create a fresh empty image of, say, 100GB in size on RBD and then > use "rbd cp" to make a copy of it, even though the image is sparse, the > command will attempt to read every part of it and take far more time > than expected. > > After reading the above thread, I understand why the copy of an > essentially empty sparse image on RBD would take so long, but it doesn't > explain why the copy won't be sparse itself. If I use "rbd cp" to copy > an image, the copy will take it's full allocated size on disk, even if > the original was empty. If I use the QEMU "qemu-img"-tool's > "convert"-option to convert the original image to the copy without > changing the format, essentially only making a copy, it takes it's time > as well, but will be faster than "rbd cp" and the resulting copy will be > sparse. > > Example-commands: > rbd create --size 102400 test1 > rbd cp test1 test2 > qemu-img convert -p -f rbd -O rbd rbd:rbd/test1 rbd:rbd/test3 > > Shouldn't "rbd cp" at least have an option to attempt to sparsify the > copy, or copy the sparse parts as sparse? Same goes for "rbd clone", > BTW. Yep, this is in fact a bug. Opened http://tracker.ceph.com/issues/6257. Thanks! sage _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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