[Techtalk] Detect if Dump used multiple tapes for backup.

[James Sutherland]

On Tue, Jun 22, 2010 at 1:31 PM, Conor Daly <c.daly at met.ie> wrote:
> On Tue, Jun 22, 2010 at 08:03:22AM -0400 or thereabouts, Little Girl wrote:
>> Hey there,
>>
>> Conor Daly wrote:
>>
>> > I'm backing up a 300Gb filesystem to an SDLT320 tape and,
>> > occasionally, the weekly level 0 dump will overflow to a second
>> > tape.
>> >
(snip)
> Mag tapes are a different kind of storage.  Basically data gets written /
> read sequentially so there's no real way to interact with a tape.  Depending
> on the software that wrote the tape, there may be a catalogue stored at the
> beginning of the tape but there's no real way to know about size stored.

How does the tape get changed? Presumably, in the overrun case, your
dump starts writing to tape #1, fills up the 160Gb (after compression),
then something goes "whoops, out of space - on to tape #2!" Even if
it's automatic, *something* must be getting told to change the tape for
the first backup to continue: could you not detect that event from logs,
exit status or whatever?


James.