On 04/03/2015 04:35 AM, Bob Williams wrote:
A subvolume differs from a directory in a number of ways. It behaves as a mountable filesystem in it's own right, and is ignored when a snapshot of its parent is made. Thus when you snapshot /, the subvolumes in /home, /opt, /srv, /tmp and various /var/* will be automatically left out of the snapshot.
If we take the scenario where instead of the sub-volumes we have mount points and mountable file systems -- a more 'traditional' (and understandable) approach -- then there is an iso-morphism here. The snapshot doesn't cover the file systems mounted because they are different file systems. "Res ipse loquitur" The only difference is that in the total BtrFS case its all the one physical space. Since, as I've commented before, BtrFS is conceived as being the who system, this all makes sense. Now I run BtrFS as the root FS, took away the sub-volumes mentioned and have them as mounted file systems. All this is done on a backdrop of LVM. I can snapshot any file system using LVM. If ReiserFS had a long term future I wouldn't even be considering BtrFS for other than SSD. As it is, I feel trapped into a future where I have to use BtrFS (to avoid the fixed inode idiocy that has existed ever since the V6/7 FS for UNIX of the 1970s) and all the complexity, and the problems that goes with complexity, of the grand Design outlook of BtrFS. The idiea of having separate volume management and file systems appeals to me. Heck, with LVM I can even use (or if you prefer, 'experiment') with other file systems (including BtrFS as a file system!). In effect LVM is a platform that does for filesystems what the virtualization tools do for operating systems. Integrating the volume management and the file system all into one, as with BtrFS, removes that flexibility. -- This message represents the official view of the voices in my head -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org