back up two macs on one external hard drive and encrypt both back ups

It sounds simple enough to me to just partition the external into two partitions so that each Mac has it's own partition, but I'm going to point you to Pondini's site, best TM reference I've seen http://pondini.org/TM/Home.html

You need either separate physical disks one for each Mac or separate partition on the same physical disk to do what you want.

Encrypted backups are only supported on OS X 10.7 or later. Is that what both Macs are running?

If you back them both up to the same partition (which usually isn't a good idea), you can't have one set of backups encrypted and the other not encrypted.

If you make two separate partitions (see Time Machine - Frequently Asked Question #4), then you can encrypt one, both, or neither, as desired.

How are you doing the backups? If you're physically switching the disk from one Mac to another, that can be a bit of a problem, too. Eventually you may damage one of the ports, and you won't get backups of the Mac that's not connected. An alternative might be to leave the drive connected to a desktop Mac, and back the other one up to the same drive via your network. That way both can back up hourly, and you don't have to do anything. See Time Machine - Frequently Asked Question #22 for setup instructions.

Pondini a Question.

Why do you say moving the drive from one Mac to another the OP will eventually damage the port? I though Apple used all the best materials on their computers? I have been plugging things in and take them out on my Mac with no problems for over a year. On my PCs that has been for years and years with no problems.

Should I not connect my TM when I need to backup and then disconnect when I am done?

Shootist007 wrote:

. . .

I though Apple used all the best materials on their computers? I have been plugging things in and take them out on my Mac with no problems for over a year.

Yes, if you're careful, you probably won't damage it. If you do it every day, or more often, there's a chance of damaging a port and/or the tiny pins on a plug.

Should I not connect my TM when I need to backup and then disconnect when I am done?

If you have a laptop, and can't back up via your network, you don't have much choice. But if you have a desktop Mac, as in Sandman222's profile, there's no need. Leave it on and connected, so Time Machine can do it's hourly backups with no intervention required.

For Firewire I have a short (12") extension to the external first in the daisy chain. I could also have the extension at the computer port, which, If I were often plugging and unplugging there (which I don't), I wouldn't have to reach all the way around to the back; doing it that way also minimizes the possibility of bending a pin when blindly inserting the cable at the back. It also takes the wear off the port.

I also have a USB extension for connecting USB devices that are frequently plugged and unplugged.

You may never bend a pin or wear out a port, but at the least this makes life far more convenient.

Hello,

This article helped me the most, it's clear and direct forward.

I highly suggest it.

http://pondini.org/TM/4.html

Enjoy!