Re: [PATCH 4/4] Btrfs-progs: exhance btrfs-image to restore image onto multiple disks

[Liu Bo <bo.li.liu@oracle.com>]

On Thu, Jun 20, 2013 at 08:39:19AM -0400, Josef Bacik wrote:
> On Thu, Jun 20, 2013 at 08:24:32AM -0400, Josef Bacik wrote:
> > On Thu, Jun 20, 2013 at 08:05:30PM +0800, Liu Bo wrote:
> > > This adds a 'btrfs-image -m' option, which let us restore an image that
> > > is built from a btrfs of multiple disks onto several disks altogether.
> > > 
> > > This aims to address the following case,
> > > $ mkfs.btrfs -m raid0 sda sdb
> > > $ btrfs-image sda image.file
> > > $ btrfs-image -r image.file sdc
> > > ---------
> > > so we can only restore metadata onto sdc, and another thing is we can
> > > only mount sdc with degraded mode as we don't provide informations of
> > > another disk.  And, it's built as RAID0 and we have only one disk,
> > > so after mount sdc we'll get into readonly mode.
> > > 
> > 
> > Um that shouldn't be happening, the restore will mask out the RAID parts of the
> > chunk tree and it should work just fine.  Are you using the most recent version
> > of btrfs-image?  If this is happening it's a bug and we need to fix it, but I've
> > restored several file systems from users with raid0/10 file systems onto a
> > single disk and it's worked just fine.  Thanks,
> > 
> 
> Well apparently I've been hallucinating because it definitely doesn't work.  I'd
> rather fix the device tree so it only restores onto one disk, since the raid
> level shouldn't matter and it does in fact get masked out.  So the only thing
> left would be to fix the device tree so the only device it knows about is the
> device we're restoring to.  Thanks,

Um, I believe that'd work and it's not hard, but I'm afraid that way we're not
able to debug bugs related to raid types?

thanks,
liubo