On 2014/05/04 09:28 AM, Marc MERLIN wrote:
On Sun, May 04, 2014 at 09:16:02AM +0200, Brendan Hide wrote:
Sending one-at-a-time, the shared-data relationship will be kept by
using the -p (parent) parameter. Send will only send the differences
and receive will create a new snapshot, adjusting for those
differences, even when the receive is run on a remote server.
$ btrfs send backup | btrfs receive $path/
$ btrfs send -p backup backup.sav1 | btrfs receive $path/
$ btrfs send -p backup.sav1 backup.sav2 | btrfs receive $path/
$ btrfs send -p backup.sav2 backup.sav3 | btrfs receive $path/
$ btrfs send -p backup.sav3 backup.sav4 | btrfs receive $path/
So this is exactly the same than what I do incremental backups with
brrfs send, but -p only works if the snapshot is read only, does it not?
I do use that for my incremental syncs and don't mind read only
snapshots there, but if I have read/write snapshots that are there for
other reasons than btrfs send incrementals, can I still send them that
way with -p?
(I thought that wouldn't work)
Thanks,
Marc
Yes, -p (parent) and -c (clone source) are the only ways I'm aware of to
push subvolumes across while ensuring data-sharing relationship remains
intact. This will end up being much the same as doing incremental backups:
From the man page section on -c:
"You must not specify clone sources unless you guarantee that these
snapshots are exactly in the same state on both sides, the sender and
the receiver. It is allowed to omit the '-p <parent>' option when '-c
<clone-src>' options are given, in which case 'btrfs send' will
determine a suitable parent among the clone sources itself."
-p does require that the sources be read-only. I suspect -c does as
well. This means that it won't be so simple as you want your sources to
be read-write. Probably the only way then would be to make read-only
snapshots whenever you want to sync these over while also ensuring that
you keep at least one read-only snapshot intact - again, much like
incremental backups.
--
__________
Brendan Hide
http://swiftspirit.co.za/
http://www.webafrica.co.za/?AFF1E97
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
