Use one external hard drive for both PowerPC and Intel backup?

[DewGuy]

I've currently got a PowerPC iMac (OS X 10.4.11) that I back up to a partitioned external hard drive using Carbon Copy Cloner. I'm thinking of getting an Intel Mac (OS X 10.5.6), would I be able to back it up to a different partition of that same external hard drive using either Carbon Copy Cloner or Time Machine?

End result would be one partitioned external hard drive with the PowerPC Mac backed up to one partition and the Intel Mac backed up to another partition, is that possible? Would/could both be bootable?

Thanks.

[mattkime]

certainly! although the drive could connect to only one machine at a time.

[yeoman]

If you don't intend to boot from the cloned copy I recommend backing up to an encrypted sparse image. Very secure and you can backup multiple machines with differing formatting. I use SuperDuper for this. If you do want to boot from that copy then you will have to copy the mounted image to another appropriately formatted drive (i.e. Apple Partion Map for PowerPC or GUID for Intel-based Mac).

[GGD]

yeoman wrote:
If you don't intend to boot from the cloned copy I recommend backing up to an encrypted sparse image. This way it doesn't matter what format is used. If you do want to boot from that copy then you will have to copy the mounted image to another appropriately formatted drive (i.e. Apple Partion Map for PowerPC or GUID for Intel-based Mac).

You can have both bootable just by using Apple Partition Map for that external drive. PowerPC requires APM to boot, and Intel will boot from either APM or GUID. Using APM on Intel does create some limitations like Bootcamp and firmware updates not working, but since it's a backup, probably the first thing you will do once booted is clone it back to an internal GUID partitioned drive in an Intel Mac.

[yeoman]

I understand that if you do this on an Intel machine booted from APM external HD this can cause software updates to be compromised, so I avoid doing this, just to be on the safe side.

[yeoman]

By the way, when I thought I was making a secure backup by not clicking "ignore permissions on the volume" I learned this meaningless, hence I now clone to encrypted sparse images.

[GGD]

Here's Apple's article on creating a "universally bootable" 10.5.

http://support.apple.com/kb/HT2595

They don't list any restrictions, but I'm pretty sure that the boot camp and firmware update restrictions do exist. I don't think there is a general problem with software updates, just firmware updates.

[yeoman]

I'm not sure if this is what I was recalling about potential software update issues but, regardless, I just avoid any possibility of incompatibility by sticking to the appropriate format and b-u to sparse images:

Quote from the Apple link above...

"Note: Support for the very latest shipping Intel-based Macs may not immediately become available via Software Update, but may be picked up in the next Mac OS X 10.5.x update. Your external disk may not be able to start an Intel-based Mac that shipped with a version of Mac OS X later than what is on the external disk."

[GGD]

yeoman wrote:
I'm not sure if this is what I was recalling about potential software update issues but, regardless, I just avoid any possibility of incompatibility by sticking to the appropriate format and b-u to sparse images:

Quote from the Apple link above...

"Note: Support for the very latest shipping Intel-based Macs may not immediately become available via Software Update, but may be picked up in the next Mac OS X 10.5.x update. Your external disk may not be able to start an Intel-based Mac that shipped with a version of Mac OS X later than what is on the external disk."

I think all that's referring to is that if you have a 10.5 on a drive (from either PPC or Intel), and update it with all the software updates, it still might not boot a very recently release new Mac.

This is because Apple sometimes has a special version of the OS that is being developed in parallel with the software update, but needs to ship on slightly different schedules to match hardware release schedules so even though their version number is the same, they are from different builds and are slightly different. Usually by the next OS update support for those newer Macs gets rolled in and everything is fine.

That really doesn't have anything to do with partition maps or PPC vs Intel. The only reason why it only applies to Intel Macs is because Apple isn't making new models of PowerPC Macs.

[DewGuy]

Thanks for all the answers so far. If I understand the responses correctly I've got a number of options. What I think I'd like to do is...

The drive is already formatted as APM. As needed I can back up my PowerPC iMac (10.4.11) via Carbon Copy Cloner to the first partition. When I get an Intel Mac (10.5.x) I should be able to connect it to the hard drive and using Carbon Copy Cloner back it up to the second partition. The PowerPC iMac will be able to boot from the first partition if necessary and the Intel Mac will be able to boot from the second partition if necessary. Correct?

Thanks.