I'm in the process of setting up a new backup system at home, and I'm feeling rather annoyed right now. The setup I wanted was thus: 1TB drive connected to my Airport Extreme Base Station with three partitions: One for my desktop boot drive Time Machine backup, one for my laptop boot drive Time Machine backup, and one for a server data backup. Now, since these backups don't need to be "deep"--it's basically catastrophic failure insurance more than "Uh oh, I deleted that last year" insurance--I figured maybe 10% more than the volume size of each would be plenty, since they're also nowhere near full. But no, it turns out Time Machine refuses to use anything that isn't at least twice the size of the volume you want to back up (this may or may not include excluded files--I haven't experimented that far). I can't find this documented anywhere other than a couple of forum threads here. First, is this in the Time Machine documentation somehwhere? Second, why the HELL does this requirement exist? Time Machine is kinda awesome, but pointless and arbitrary limitations like this annoy me rather severely. Third, this seems to really limit the usefulness of TM on large drives, since you'd need to find one twice as big to back up to... or does the limitation not exist with local volumes? As a workaround I ended up just making two partitions, one being the size of what would have been the two time machine backups. I can then select that from BOTH of the machines, and since it's twice as large as the boot drive on either, TM doesn't complain (the sparse images created don't conflict, apparently). Hopefully once the sparse images expand to fill the available space they'll each start deleting chunks of their own backups to stay happy, though I'm afraid instead it's going to choke and I'll end up having to ditch TM entirely for a 3rd party solution. Is there some other solution I'm missing here?