If you are creating archives in which you will want to extract individual
or groups of individual files (as opposed to restoring the whole backup),
then you are better off backing up in small amounts eg. in one backup
session, backup up /usr, then another backup session backup /home, then
/var etc... Each different directory will then be in separate volumes. Then,
if you want to restore a file from /var, taper can advance the tape directly
to the volume where /var is. If you had backed everything in one session,
the only way taper can find files in the /var directory is to read the
whole backup in which can take a while.

If you are only archiving your hard-disk to restore the whole thing in
event of a crash, then the above is not necessary.
