Re: About btrfs chunk tree backups

[Josef Bacik <josef@redhat.com>]

On Tue, Mar 08, 2011 at 12:14:05PM +0800, Miao Xie wrote:
> On Thu, 3 Mar 2011 07:37:25 -0500, Josef Bacik wrote:
> > On Thu, Mar 03, 2011 at 05:01:00PM +0800, Miao Xie wrote:
> >> Hi, Chris and Josef
> >>
> >> Recently, I am interested in chunk tree backups, which is described in
> >> Project ideas web. But I found it is hard to be implemented.
> >>
> >> The description said "make the mappings discoverable via a block device
> >> scan so that we can recover from corrupted chunk trees", I think it is
> >> hard to find the boundary of each stripe, which is the constituent of
> >> the chunks, via a block device scan according to the current on-disk data
> >> structures. And besides that, even though we find the stripes of each
> >> chunks, we still don't know the order of the stripes in one chunk. So
> >> I think chunk tree backups is hard to be implemented.
> >>
> >> Maybe I made some mistakes in understanding this project idea?
> >>
> > 
> > We talked about this some earlier this week.  This will require a format change,
> > basically we need to put down some metadata at the start of every chunk so that
> > we can scan the disk and find the chunks.  This could probably be done in a
> > backwards compatible way, we just need to make sure the space for the block
> > thats used is taken up in the extent tree so old kernels don't write over the
> > block.  Thanks,
> 
> Hi, Josef
> 
> Is anyone implementing it now? Maybe we can help him to do some work.
> 

Not that I know of.  Thanks,

Josef