I am looking for a removable disk drive that will allow me to create
backups from my Apple PowerBook G4.

The total capacity of my system is 140GB. Although this is only
partially filled at present it will probably be filled in the future.
Thus I need a system that can handle a large amount of data.

Requirements
   1. The drive needs to be compatible with Mac OS X version 10.2 or
higher.
   2. The drive should connect to the computer over the FireWire bus
(IEEE 1394).
   3. The disks should have a large capacity i.e. > 4 GB.
   4. The disks should be cheap i.e. < $10 each.
   5. The disks need to be durable i.e. they will not deteriorate in <
25 years.
   6. The write speed should be high so that backing up many GBs will
not take excessive amounts of time.
   7. The read speed should be high so that restoring from backups
will proceed quickly.

Note: Write speed is much more important than read speed since backups
are performed daily to weekly while restores are conducted only when
there has been data loss. Rewrite speed is irrelevant since backups
will not be altered but rather archived. In fact it is a plus if disks
are only writable once.

Optional Criteria (use to narrow results if there are more than 10)
   1. Should be compatible with Dantz Retrospect Express. If you
cannot find any that are then ignore this condition.
   2. The disks are readable in drives that can read DVD-ROM or
DVD-RAM formats.
   3. The disks are not sensitive to magnetic fields, moisture, or
shock.

A very cheap alternative *if* you have a desktop G4 Mac with a largish
hard drive (I have 2 x 60gb), you can backup the laptop to that with a
simple firewire lead. (That's what I do). The advantage of this is you
can store the whole backup in one place instead of over multiple
disks. Fast to back up, fast to retrieve, easy to navigate the backup.
But the hard drive is not going to last 25 years. A solution is to
obtain a larger capacity hard disk every 2-3 years and copy the
swelling contents on to the fresh hard disk before hard disk failure
occurs with old age. The contents of my 40mb hard drive were
transfered to 750mb > 1.2gb > 10gb > 20gb > 60gb so the data doesn't
languish on an old drive.
regards lot-ga

I have had good luck with cheap firewire drives from:

http://piranhatech.com/index.asp

Here are high capacity Firewire drives:

http://piranhatech.com/products/displayproducts.asp?catid=1009&subcatid=2037&manufacturer=HIGH+CAPACITY

I use a UNIX program called psync to sychronize my drive to the backup
drive. It works pretty well.

honestly, there's no such thing as a cheap, reliable backup solution
that lasts forever. as technology grows and changes, like the other
posters stated, you have to upgrade. about every 2-5 years. Now, using
the firewire bus on your mac, you can move a fair amount of data
fairly easily. Tape drives work but can be a pain. tape can also
degrade. DVD-R is also decent for storage purposes but the discs take
up space, money, and are write once. For a hard drive based solution,
as an apple tech, I bought and recommend LaCie's D2 drives. They're
cased in Aluminum, almost dead silent(no fan), and very well built.
They're 120GB @ 7200 RPM which is easily enough for things like
video(lacie claims that when using they're drives with video editing,
you wont get any frame drop). So, for almost any realistic backup
purposes, LaCie's D2 drives are Grade-A. Not to mention that they run
2-3 hundred depending on where you buy. Not a bad deal for a top of
the line storage solution. Hope this helps!