Backup and Storage Advice Needed

The plan you're outlining sounds like it'll work fine, but I'll offer my rather similar setup as an example:

I have a MBP, an iMac, and an HTPC Mini using a single AEBS as the network hub for everything (Mini and iMac wired, MBP wireless).

I run my setup with the Mini acting as a backup and file server for everything else. It has two external drives; one contains all "working" files (media, documents, etc) that are accessed directly by other computers in the house (and it, when it's playing music through or video directly to the stereo or TV). The other is a backup drive that contains three partitions--a relatively small partition to be used by Time Machine over the network from the other two Macs, and a third for backups of the main data drive.

This setup has worked flawlessly for me; the network Time Machine disks work smoothly (although wireless backups from the MBP are slow enough, and interfere with my wireless mouse, that I don't have those running automatically, only on-demand), and even in the event of severe disk corruption or a catastrophic failure of the case (rather than the drive) I've got a separate hardware device with a full backup. It's also possible to only keep the online data drive on FW800; the backup drive can be a budget USB2 disk, since speed really doesn't matter.

Now, because my wife keeps me on a shoestring budget, I only have single-drive cases for both of those, but if I had more money to throw at it, I'd probably be running a larger RAID5 as the on-line drive, and limit backups to the subset of files I really care about, leaving the rest to be semi-protected by RAID5, but vulnerable to disk corruption or a failed case.

The advantage of this setup over using a Time Capsule is that you can use any cheap USB external in place of the time capsule, and it's easy to upgrade (or replace in case of drive failure); the Mini has plenty of CPU to spare, so it runs at least as fast as, if not faster than, a Time Capsule when using a gigabit ethernet link. I actually tried using the disk sharing feature of the AEBS I have with a USB external, but it repeatably corrupted the backups after some period of time (and was very slow on top of it), so far as I can figure because there just isn't enough CPU in the thing to handle that number of disk transactions.

It's going to be a little more power hungry than using a Time Capsule, but the mini is pretty thrifty, and if you regularly use it for background downloading or media serving (networked iTunes) it's a worthwhile tradeoff.


[Full disclosure: Due to hardware constraints and limited budget, plus geekiness, my setup is technically using eSATA for the data drive and FW800 for the backup, because I FrankenMini'd my Mac to externalize the SATA ports. The data drive also has a small boot partition on it, since there's no internal drive (or optical drive) in the Mini. And I have a stack of three bare 2TB drives full of my ripped DVD collection that I occasionally use with a toaster-style dock, which keeps my data needs on the main drive pretty light, so a single 2TB is plenty.]