On Wed, Sep 4, 2019 at 2:20 PM Hugo Mills <h...@carfax.org.uk> wrote: > > On Wed, Sep 04, 2019 at 04:04:44PM +0200, Piotr Szymaniak wrote: > > On Wed, Sep 04, 2019 at 12:03:10PM +0300, Andrei Borzenkov wrote: > > > On Wed, Sep 4, 2019 at 9:16 AM Swâmi Petaramesh <sw...@petaramesh.org> > > > wrote: > > > > > > > > Hi list, > > > > > > > > Is there an advised way to completely “clone” a complete BTRFS > > > > filesystem, I mean to get an exact copy of a BTRFS filesystem including > > > > subvolumes (even readonly snapshots) and complete file attributes > > > > including extended attributes, ACLs and so, to another storage pool, > > > > possibly defined with a different RAID geometry or compression ? > > > > > > > > > > As long as you do not use top level subvolume directly (all data is > > > located in subolumes), send/receive should work. > > > > > > > The question boils down to getting an exact backup replica of a given > > > > BTRFS filesystem that could be restored to something logically > > > > absolutely identical. > > > > > > > > The usual backup tools have no clue about share extents, snapshots and > > > > the like, and using btrfs send/receive for individual subvols is a real > > > > pain in a BTRFS filesystem that may contain hundreds of snapshots of > > > > different BTRFS subvols plus deduplication etc. > > > > > > > > > > Shared extents could be challenging. You can provide this information > > > to "btrfs send", but for one, there is no direct visibility into which > > > subvolumes share extents with given subvolume, so no way to build > > > corresponding list for "btrfs send". I do not even know if this > > > information can be obtained without exhaustive search over all > > > extents. Second, btrfs send/receive only allows sharing of full > > > extents which means there is no guarantee of identical structure on > > > receiving side. > > > > So right now the only answer is: use good old dd? > > If you want an exact copy, including all of the exact UUIDs, yes. > > Be aware of the problems of making block-level copies of btrfs > filesystems, though: > https://btrfs.wiki.kernel.org/index.php/Gotchas#Block-level_copies_of_devices
This might be fixed now. Anyone want to test it? With a recent kernel of course. *runs away fast in case it isn't* -- Chris Murphy
