Darn good question,
I don't quite know about this, however if you have OS X Server, you should be able to set it up.
on the remote Mac you'd need to have file sharing set up, then you might be able to mount the remote disk as a timemachine source.
I'd try backing up to the external drive _locally_ first, then moving it offsite. It should make the backup go much quicker and if your .sparcebundle is on the disk i'd hope that your machine mught recognize the source as a TM set and let you use it.
It all comes down to TM being quirky.
Thanks for your reply. Yeah I'm currently creating a 2nd backup and taking it offsite, but this can be a bit of a pain, especially when half the time I only remember to do it when I'm home and lying in bed!
But if anyone knew how to set up a remote system as the time machine, that would be great.
There must be a relatively easy way to do it as the office used to have this set up on their PC's and I would have thought that Mac's should be able to do it also, being far superior and easier to use beings that they are! ha
My first thought is that TM is really a basic backup aimed at average home users, not servers. You may be able to do what you're trying, but you may be setting yourself up for frustration. TM can be modified with a bit of work, but I'm not sure that's what I would try to do, particularly if the data on the server is valuable to you. In my experience TM was great when it worked, but when it coughs up errors, there aren't a lot of options. I gave up on it for home use, and I've never used it for a server. I'm sure some people have had success with it, but I'm not a big fan...
Look in to CCC or SuperDuper, as those are much more flexible by design. Perhaps a commercial online backup such as CrashPlan or Carbonite might make sense as well, as they are not particularly expnsive for the service they provide.
Just my $.02, YMMV,
Time Machine uses Bonjour to broadcast and discover Time Machine enabled shares or drives. You can't AFAIK specify a Time Machine destination using TCP/IP or DNS. Getting Bonjour to work over a WAN connection is possible but requires whatever you're using at the network's edge to support it. Even then I doubt if it will give you problem free backups? WAN connections are - in most cases - slow and subject to fluctuation and interruption.
Apart from that I have to agree with Jeff's opinion.