Well, depends on your load at the time you are trying to run the backup.
If your system is already taxed doing software compression could make your
backup take longer. If one of your other goals on your list is to reduce
your outage window due to backup this may not be the way to go.
Another thing to consider, since you are re-evaluating your backup anyway
is virtual tape devices, and I am not talking about CRTDEVTAP
DEVD(TAPVRT01) RSRCNAME(*VRT). What we are looking at is some appliance
which emulates a tape drive on your i that you perform your backup to. The
output actually goes out over the comm line to someplace like Iron
The reason I mention this is that if you're thinking about obtaining a
device which does hardware encryption, and this appeals to you, why tie up
money in an intermediate solution?