For those with backup tapes (and I just bought and installed a Seagate one for my FreeBSD box) I want to know how to get the most out of each tape by placing multiple backups on each tape (potentially 20GB). Please correct me if I'm wrong:

First, retension the tape:
# mt retension

next, turn on compression so I get the full 20GB space:
# mt comp on

next, complete a specific folder backup (no rewind set)
# tar cvz /home

Ok - now I need help:
set an end-of-file marker for the tape location???
# mt weof 1

carry on with next folder backup
# tar cvz /usr

continue this until backup / tape completed!

Ok - Then to get back???:
move to correct folder location on tape, e.g. /usr
# mt fsf 1

untar files
# tar xvz

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Could someone with tape backup experience let me know if this is right or where I've gone wrong? MANY THANKS!!!!

I normally only use one tape per tar backup with my Exabyte 8505XL so I am really interested in finding out if this is correct.

I have found a successful solution; it can be a bit complicated, but it does work:

Notes, see which device node I have used:
basic device /dev/ast0
No rewind /dev/nast0

Retension tape and compression on are correct; complete first backup with no-rewind:
# tar cf /dev/nast0 /home/root

now set the end of file marker, with rewind:
# mt -f /dev/ast0 weof 1

Ok - here's where it get interesting, you now need to forward the tape to the right location for the next archive (no-rewind) - HOWEVER, I found that when this command is issued, the "mt" program does NOT wait for the device before returning control to the command line ~ be mindful of this in your shell scripts, etc:
# mt -f /dev/nast0 fsf 1

Now do the next archive and write the "weof" marker:
# tar cf /dev/nast0 /var/
# mt -f /dev/ast0 weof 1

Do this as many times as required, but make sure you move the tape sufficient times forward each time, eg. after my "/var/" backup the tape will rewind, therefor I will have to move the 2 files foward to do the next archive (eg. mt -f /dev/nast0 fsf 2)

OK - Now to get it back!!! Easy peasy! Let's say I want the var directory back; first move to the right location then untar as usual:
# mt -f /dev/nast0 fsf 1
# tar xf /dev/ast0

Hope this helps everyone!!!!

Hey, it's Friday night so I'll get crazy and play with this tonight at home. That's right, I live life on the edge!