[G4] new hard drive issue

[Joseph B. Gurman]

     Keith Whaley wrote:

>Slightly different flavor of hard drive question, but I do need an answer...
>
>I have a 2002 Power Mac G4 tower, OS 10.2.8, 80 GB H.D.
>
>For backup purposes, I still need something to receive the data -- like
>another H.D.
>Since I only have something like 6 GB of total data on the existing H.D.
>and the likelihood of ever surpassing even 10 GB is very slim, is it
>feasible to back up what content/data I do have on a 20 or 40 or 60 GB H.D.?
>Or must the receiving H.D. be at least as big as the drive being backed up?
>
>I don't particularly care about the cost of the new B.U. H.D., but if I
>need to look for a H.D. that has at least as large as 80 GB, I need to
>know that going in...

and Jesper Bylund answered:

>No. The backup drive only have to be as big as the data you want to
>backup. The same thinking as with iDisk: If you have 100MB space you
>will be able to backup 100MB of data.

     Well, maybe; it depends on what sort of backup you want/use. If 
you use something (e.g. ditto or psync) that simply images the disk 
as it is today, all you need is the volume currently in use. If you 
use an incremental backup application (such as Retrospect), it allows 
you to access an image of however your disk looked on any backup date 
since you began backing up --- so you'll presumably need more space 
than is used on your current hard drive. How much more depends on how 
much "thrash" there is in your files --- do they change a lot from 
day to day, while maintaining about the same total number of blocks, 
or are they pretty much the same things --- and on whether you back 
up useless files such as browser cache files.

     And finally, a holdover from the days when disk drives were too 
expensive to be given away as prizes in Crackerjacks packages, some 
backup software will allow you to compress the backup image (in 
software, and thus with a performance hit), so you might need _less_ 
space than you use on your current drive.

     There: I made a simple answer complicated. Just like real life, 
except for politicians.

						Joe Gurman
-- 
"I love deadlines. I love the whooshing sound they make as they go by."
                                                             - Douglas 
Adams, 1952 - 2001

Joseph B. Gurman, NASA Goddard Space Flight Center, Solar Physics
Branch, Greenbelt MD 20771 USA