On Mon, 2005-12-05 at 16:11, Bryan J. Smith wrote:
> Joshua Baker-LePain <jlb17@xxxxxxxx> wrote:
> > Amanda can easily be run in a backup-to-disk-only mode.
> > And it'd be trivial to manually tape some of those images
> > for off-site storage. Doing that within amanda (i.e.
> > backup-to-tape while also leaving images on disk)
> > is a feature folks have talked about.
>
> Excellent!
>
> The question is how seemless is it? Can they stream out
> their images into a tape archive? It should be possible.
The tricky part is that amanda mixes up the filesystems on tape
in no particular order and keeps an index online to tell you
which tape(s) to insert when restoring. When it flushes the
disk copy out it adjusts the index for the new location so
without a patch it won't use the disk copy even if you saved
one. There is a tool for rebuilding the index from the tape
if necessary and you can figure it out by hand as a last
resort but I don't think there is one to look at the holding
disk again.
> What about importing back a stream from a tape archive into a
> disk image? That also should be possible.
>
> The ability to make verification and restores -- the two most
> overlooked details of off-site backup -- are what make VTL
> systems/approaches most lauded.
Amanda uses dump or tar for the backups and adds one extra block
as a header to each backup. You can strip off the header with
dd and restore with dump or tar alone. It was a nice system
15 years ago but hasn't had a lot of development since. It
has one big flaw in that it can't split a single filesytem
backup across more than one tape even though it can do many
hosts/filesystems in one run splitting different backups within
the run over different tapes. With todays big disks that's probably
fatal.
--
Les Mikesell
lesmikesell@xxxxxxxxx
