Multiple clones on same partition?

[ninobravo]

Simple question, with probably an even simpler answer, but can I clone multiple drives to the same partition?

I just got a 320 GB external drive and I'm trying to figure out how many partitions to create. I'd like to have one clean, bootable OS install with just disk utilities (Systemworks, DiskWarrior, etc) for emergencies, one with a clone/backup of my present system, and another clone/backup of my girlfriend's system (since she doesn't have any backup options). The rest of the external drive would just be extra storage.

I'm supposing that means I'll need four partitions?

Then the next question is, how big for each?

[dnanian]

Nino:

It depends a lot on whether you want the copies bootable. If you only want ONE bootable one (or two -- whatever), you can make a partition for that, and then share the other partition by storing a series of sparse images, one for each full copy.

There's a FAQ entry that explains how; since the sparse images will grow to accommodate the data stored in them, you'll make efficient use of the storage, and don't have to worry about the exact size of the partition so much.

If you do want to partition -- which is the best thing, but not required -- you'd make the partition the size of the maximum amount of data you plan to grow the drive to. So, if it's a 60GB drive, but you think you'll never store more than 40GB on it, I'd make the partition 40GB+10% or so.

Make sense?

[ninobravo]

Hmmm... sort of.
So if I want the clones to be bootable, then they should live on their own partition?
Ideally, I do want each of the clones to be bootable, so that I can always revert to them in case of a system failure. Same for my girlfriend's system, and of course, the clean "rescue" system install. But you're right, I don't want to waste drive space by partitioning too much.
These sparse images sound like data backups, but not bootable backups. I guess as long as the "rescue" system is bootable, and can repair any potential issues that may arise, I guess all I'd need is to backup my data in order to be able to restore it after repairing.

[dnanian]

If you want your copies to be *directly* bootable -- that is, bootable *before* you restore them to their original location -- they have to live on their own partition.

So -- they are bootable backups: they're just not bootable until they're restored. Since you've got a system you can boot from, that's not a *huge* disadvantage...

[ninobravo]

Sounds good. Theoretically, then all I'd need to partition for is the "rescue" drive, and use that to fix, and restore from the sparse image clones.
I think that may be the way to go...

[dnanian]

That's right. You can also use your OSX install disc: check out section 5 of the User's Guide for more!

[sjk]

Theoretically, then all I'd need to partition for is the "rescue" drive, and use that to fix, and restore from the sparse image clones.
I think that may be the way to go...I've been satisfied using SD! for backing up my iMac G5 boot volume to a bootable volume and everything else to sparse images on two FW drives. I'd be wasting too much space, or not having enough for everything I want backed up, by backing up to separate volumes. I've also got a "scratch" volume on an iBook G3 that can be used in FW target mode, if that's ever necessary for some reason.