>>> Andrei Borzenkov <arvidj...@gmail.com> schrieb am 18.05.2021 um 13:05 in Nachricht <CAA91j0WgWgK=me=vjkxv9ck00d-chyjo7jju1gewssc7o6e...@mail.gmail.com>: > On Tue, May 18, 2021 at 1:52 PM Ulrich Windl > <ulrich.wi...@rz.uni‑regensburg.de> wrote: >> >> Hi! >> >> I thought using the reflink feature of OCFS2 would be just a nice way to > make crash‑consistent VM snapshots while they are running. >> As it is a bit tricky to find out how much data is shared between snapshots, > I started to write an utility to examine the blocks allocated to the VM > backing files and snapshots. >> >> Unfortunately (as it seems) OCFS2 fragments terribly under reflink > snapshots. >> > > Does it cause any real problem? > ...
As we are running on SSDs now, probably not (I didn't measure performance), but in the past using spinning disks that probably was a problem. Still I think gathering multiple spread blocks is somewhat inefficient in the block device layer. >> >> So I wonder (while understanding the principle of copy‑on‑write for reflink > snapshots): >> Is there a way to avoid or undo the fragmentation? >> > > If you understand the principles you can answer it yourself. To avoid > fragmentation you need to avoid reflink. Well, if there is no "defragment utility", I might just copy the image to t a new file from time to time... Regards, Ulrich > _______________________________________________ > Manage your subscription: > https://lists.clusterlabs.org/mailman/listinfo/users > > ClusterLabs home: https://www.clusterlabs.org/ _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
