Re: Incremental backup for a raid1

[George Mitchell <george@chinilu.com>]

Michael,  I am currently using rsync INSTEAD of btrfs backup tools.  I 
really don't see anyway that it could be compatible with the backup 
features of btrfs.  As I noted in my post, it is definitely not a 
perfect solution, but it is doing the job for me.  What I REALLY want in 
this regard is n-way mirroring to get me out of the simplex trap 
completely.  At that point, I can have more confidence in btrfs snapshop 
capability.

On 03/15/2014 04:35 AM, Michael Schuerig wrote:
> On Thursday 13 March 2014 17:29:11 George Mitchell wrote:
>> I currently use rsync to a separate drive to maintain a
>> backup copy, but it is not integrated into the array like n-way would
>> be, and is definitely not a perfect solution.
> Could you explain how you're using rsync? I was just about to copy a
> btrfs filesystem to another disk. That filesystem has several subvolumes
> and about 100 snapshots overall. Owing to COW, this amounts to about
> 1.2TB. However, I reckon that rsync doesn't know anything about COW and
> accordingly would blow up my data immensely on the destination disk.
>
> How do I copy a btrfs filesystem preserving its complete contents? How
> do I update such a copy?
>
> Yes, I want to keep the subvolume layout of the original and I want to
> copy all snapshots. I don't think send/receive is the answer, but it's
> likey I don't understand it well enough. I'm concerned, that a
> send/receive-based approach is not robust against mishaps.
>
> Consider: I want to incrementally back-up a filesystem to two external
> disks. For this I'd have to for each subvolume keep a snapshot
> corresponding to its state on the backup disk. If I make any mistake in
> managing these snapshots, I can't update the external backup anymore.
>
> Also, I don't understand whether send/receive would allow me to
> copy/update a subvolume *including* its snapshots.
>
> Things have become a little more complicated than I had hoped for, but
> I've only been using btrfs for a couple of weeks.
>
> Michael
>