Backup across multiple DVD's

[Felipe Figueiredo]

Dave,

On 8/2/07, Dave M <DaveM at mich.com> wrote:
> Dar and KDar work well if the slice sizes are kept reasonable. When doing

So a 3GB backup in a single slice is not a reasonable size? Why not?
Is there a rule of thumb for choosing slice sizes?

> DVD backups I do 400Mb slices with 40Mb par2 files. They fit evenly on a

So for a 5GB backup you would have some 10 slices on the first disk,
and a couple on the second. Sorry, I can't see how this is helpful (I
mean, instead of two slices), especially because of the problem you
mentioned below (of slices not being standalone).

I would add that with this approach you'd be somewhat slowed down
because of overhead for accessing many files. Not sure how much slowed
down, though, but since optical media is already slow compared to
HDs...


> DVD and work around the "no new sessions past 4Gb"  problem with growisofs.
> So I can still fill up a DVD if I have enough slices.
>
> My one big complaint about Dar is the fact that slices are not stand-alone.
> You must have the whole set of slices or an extracted catalog from the
> whole set of slices in order to recover anything. I think that is a major
> vulnerability since backup media can have problems. And tape, CD and DVD
> media are especially vulnerable to data errors.

Agreed. Which is why I consider sticking with minimal slice number
(respecting, for example, maximum 4GB file size limitation, for 32-bit
systems). Also, differential backups are standalone, so if you manage
to make single-sliced backups, you get to minimize change of
encountering the bug you mention.

regards
FF