Re: [flexbackup-help] Determining Tape Drive Size

[Simon M. <sim...@ch...>]

> I am writing some [minimal] oss software, after 5 years of just using i=
t.
>
> Background:
>
> Simplified "unmanaged" distributions like e-smith / SME server
> (www.contribs.org) are not supposed to require a full-time admin.
>
> Once setup by someone competent, they require nil maintenance unless
> something breaks.
>
> I am unsatisfied with the backup solutions available.  Hard drives are
> now large, but large tape drives are expensive, especially for the s in
> SME.
>
> I like the DDS2 tape drives that are almost free and plentiful around
> here, as are tapes used once only.
>
>
> Problem:
>
> The system does not provide effectively for incremental backups, and in
> any case that would require sensible tape management.  I want a full
> nightly backup on a new tape each night.  However, the data set is too
> large for the tape, and restoring can be complex.
>
> Solution:
>
> 1) Get flexbackup to prompt for the next tape via email.  I couldn't
> figure this out, and in a full backup every 24 hours you may find a tap=
e
> drive which is permanently in use.
>
> 2) Split the backup into five flexbackup sets, named by the days of the
> week.  Call flexbackup with date +%A as the set name.  Define the sets,
> each small enough to fit on a certain part of the drive.  Automate this
> using bash scripts and du, and a script to detect when the sets are too
> large to fit on the tape
>
> Question:
>
>    How can I determine the capacity of a tape in a generic fashion?  I
> want this to run on any e-smith machine.

I think it's almost impossible to determine the capacity of a tape withou=
t
disabling hardware compression, which is on by default.
Just yesterday I've built an rpm package of a tool I discovered which may
be exactly what you want. It's called SpanTape and is available here

http://sokrates.mimuw.edu.pl/~sebek/spantape/

and the rpm is here
http://www.invoca.ch/pub/packages/spantape/

It works like dd but outputs to SCSI tapes and lets you span the output t=
o
multiple tapes. I didn't use it yet but it sounds very useful.

Regards,
Simon