I'm a big fan of [CrashPlan](http://crashplan.com), which is sort of like a platform-agnostic Time Machine with full internet support (minus the pretty star field graphics). I use it to continuously monitor and back up two machines (Mac Pro and MacBook Pro), and when I'm travelling, but MacBook Pro continues to back new files up -- to a machine in my closet -- through the internet.
I have CrashPlan+ licenses for the two machines I back up. CrashPlan+ doesn't exist anymore, but it seems to give me some of the features of CrashPlan Pro like compression, encryption, and real-time monitoring of file changes.
Now, for the bad news: CrashPlan works really well when I have one machine backing up to another, but fails miserably when I have two machines backing up one machine. My MacBook Pro always backs up perfectly to the destination, but my Mac Pro stops after some time (usually works until I stop the initial backup, at which point it never starts up again).
- starting and stopping the CrashPlan engine - setting each instance of CrashPlan to a different port - reinstalling CrashPlan - reinstalling the OS - following directions sent from CrashPlan support (multiple times)
Each time, CrashPlan support says that it "must be a network issue," but can't figure out why it's not working. I think it might be because I'm backing up multiple terabytes.
A few days ago, I realized that I was being stupid because I'm backing up my Mac Pro to a NAS volume that is mounted on the server. The server isn't even necessary for my Mac Pro backup, since the 55-lb machine never leaves the house! So I'm now pointing my CrashPlan backup directly at the volume on the NAS box. The MacBook Pro is still happily backing up via the server.
I hope it works.