Tape Backup Recommendations

Ian Pallfreeman ip at mcc.ac.uk
Mon Dec 4 11:22:18 GMT 2000

> I am looking for a tape backup solution for a large (100+ GB) database.
> Preferably rack mounted using an external SCSI connection to the rack
> mounted FreeBSD backup server. 
> I am considering a DLT autoloader of some sort, and the FreeBSD release
> notes do suggest that SCSI autoloaders should be supported. I have no
> experience of autoloaders, do they look like continuous tape to the OS,
> or do I need to do some magic to use them? 

You'll need magic of some sort, but what you'll need depends on the autoloader
you've got. 

FreeBSD supports tape changing robots. Basically it allows you to select a
tape from your collection, get the robot to insert it in the drive, remove
it when you're done and put it back in your collection. See the manpage on
chio for details.

Alternatively, for the simpler stackers, you can use the "eject on close"
tape flavour (/dev/ersaN). These stackers, in "nearly manual" mode, will
load the next tape from their cartridge when you eject.

With either of these, you'll need some software to deal with the tape change;
generally, the stock utils don't have what's needed. From what I've been told,
amanda is a good dumping system; it's in the ports collection.

What FreeBSD doesn't have is the equivalent of the Solaris "l" option to
dump(8). This is a neat but dirty way around the problem of stackers needing
manual intervention -- at EOT, it ejects, then waits around for a while trying
to reopen the tape device, which hopefully will then contain the next tape
from the stacker, thus allowing dump(8) to treat the entire stack of tapes
as one long tape. I mention this because I have a patch to make FreeBSD dump
do this, almost exactly the same as the Solaris version, and about half a
dozen crappy HP1553 DAT autoloaders to play with.

For any other software, in order to treat the entire contents of your 
autoloader as a continuous tape, you'll need some extra scripts to handle
the change of medium.



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