Recommended Partition Sizes?
 

I've got a 1.83 GHz Intel iMac, running OS 10.5.5, with a 233 Gb internal HD and a 112 GB external HD attached. The external HD is not partitioned. I'm using SD to backup my iMac (I currently have lots of free space on my iMac). I'm purchasing a 1TB external HD, and I'd like to use both SD and Time Machine for backups. I'd also like to make use of some of the external space for pics, music, & movie storage. Any recommendations on partition sizes for the 1TB HD?

Well, the SD! one should probably be 233GB or so. The others are kind of up to you!

Dave, how much "or so" does one need above and beyond the internal drive's nominal size to be sure that the SD! partition is sufficiently large?

There's no way for me to know: it depends on the types of operations that you do. Usually, 233GB should be just fine.

I realize that the numbers (e.g., 233 G) may not be exact from drive to drive (who knows...perhaps one should allow for a 5% difference), so (I assume) that's part of why you said "or so." But what other kinds of "operations" might affect how big one should make the partition?

See the Troubleshooting section of the User's Guide for a general discussion of disk full errors and what contributes to them...

OK...

It sounds like it might be advisable to provide additional space to allow for potential problems (how much, there's no way of knowing), as well as some amount of "overhead" for “working space” during copying, to avoid having to do an "Erase, then copy…" Though how much one should allocate for either is impossible to predict, do you have any sense (based on experience) what a reasonably "safe" percentage might be...or is it simply too unpredictable to even venture an "on average" guess?

If I had a rule of thumb here I would have provided it. :)