[CentOS] OT - Linux NAS for Windows Environment

Wed Feb 1 13:53:56 UTC 2006
Les Mikesell <lesmikesell at gmail.com>

On Wed, 2006-02-01 at 04:49, Karanbir Singh wrote:
> >>>I think there are still problems with LVM2 snapshots.  
> >>
> >>we're hoping to see a major improvement in that situation ( lvm2 / 
> >>kernel 2.6 / snapshots ) with the CentOS 4.3 release. not too far now :)
> > 
> > 
> > Do you know if it is possible to image-copy a snapshot off
> > to another system?  A backuppc archive contains so many hardlinks
> > that normal copy techniques are not practical.  I currently
> > raid-mirror to external firewire drives that are rotated offsite
> > periodically, but it would probably work better to freeze an
> > LVM snapshot and copy that instead.
> > 
> you can reverse mount and add-as-share the snapshot, over whatever 
> service you like ( smb, ftp, http-web-dab, nfs ) and backup using 
> whatever means you like.

That's not what I meant. It takes an impractical amount of time
to copy the files from a mounted backuppc archive with millions
of hardlinks.  I'd like instead to do an image copy of the
partition block device either to a physical disk partition
or a file that could be loopback-mounted later if needed.
This should be the same as copying real partitions with
dd, except I'd want the frozen state of the snapshot so
the filesystem could remain active while the copy runs.
Someone on the backuppc list has mentioned doing this so
I think the snapshots present a normal-looking block
device interface - but I think they've had trouble with

It would be even nicer if you could use rsync to update
a remote image using only the bandwidth needed to transfer
the differences (again a horrible thing to do through a
filesystem with millions of symlinks).  Does the size of
a snapshot and the locations of the used portion stay the
same between snapshots?

   Les Mikesell
    lesmikesell at gmail.com