Hi,
I few days back I asked the following question
>
> Dear Managers,
>
> we've recently switched our main backup machine from VMS to Unix
> (V4.0B). Our backup medium is a Quantum DLT4500 with a media changer
> unit. Both devices have been entered into the /etc/ddr.dbase (see
> below). Due to financial reasons (my employer being an university, after
> all...) I'm forced to do the backups with tar. The current strategy is to
> tar each filesystem individually onto the DLT, with each filesystem
> having a size of about 10GB (although we've also a 65GB RAID, but that's
> another story...). My problem is that the DLT does not appear to switch to
> the next tape when the EOM is reached.
>
> Therefore:
>
> 1. How do I configure the DLT/Changer such that it switches automatically
> between the tapes in a tapeset?
>
> and/or
>
> 2. I could switch manually between tapes, but how do I do that
> softwarewise so that I can run my backups overnite?
>
> Thanks for your help,
>
> Joern Wilms
> wilms_at_astro.uni-tuebingen.de
>
and soon got very good and helpful replys from
Jim Belonis <belonis_at_dirac.phys.washington.edu>
Susan Rodriguez <SUSROD_at_HBSI.COM>
Alan Rollow <alan_at_nabeth.cxo.dec.com>
Mitch Bertone <mbertone_at_gtech.com>
Below I summarize their answers:
1. with
mt rewoffl
the tape is not only rewound, but also ejected and the next tape is put
into the drive. Indeed, it works! (although I don't know yet what
happens when the last tape is ejected -- hadn't the stamina to wait and
check that...)
Several people recommended using expect
together with tar to automatically catch tar's requests for
a tape change by running the above command (plus a sleep). This way the
production of tar savesets larger than one tape is possible. Others
recommended to just make sure that individual tar's don't fill up the
tape and then issue the mt-command between the tar-commands. I'll
probably adapt the latter approach in the future except for the backup
of our 65GB RAID.
2. Apart from informing me about `mt rewoffl' several of the answers I got
contained comments about the choice of backup-tool used (tar in my
case). Some people strongly recommended (v)dump instead of tar, and one
pointed me to a quite interesting paper on different backup strategies
(
http://www.phys.washington.edu/~belonis/backup-torture.ps [although
this paper is from 1991, most of the information might still be valid --
except for gnu-tar...]). vdump also appears to be able to handle
multi-tape backups including sending the appropriate commands to the
media changer.
3. Some people recommended commercial or public domain software to do
backups and/or switch the tape. I haven't looked into these yet. Most of
the commercial products unfortunately appear to be too expensive for use in
a university environment. Here are the products mentioned (in no
particular order)
seltape (tape changer, available for SGI Irix).
Boston Business Computers VMS Backup emulator for Digital Unix.
Trovli
CA Unicenter.
Thanks again to all who answered, this list has again proven to be VERY
useful!
Cheers,
Joern
Received on Thu May 14 1998 - 08:32:07 NZST