rsync bottleneck

[diburim]

Hello,

I'm planning to use rsync for backup a lot of nodes to one rsync server over
wan.
I'm aware of the fact that on big directory tree rsync will consume a lot of
memory
and some time even hang.
Do you have any estimation on how many rsync client can work with one server
at the same time ?
I can control each client bandwidth. What will be the bottleneck on the
server resource ?
Is there any role of thumb.
My server running Linux 1Gh Pentium cpu and 512 Mb memory.
Please share your experience.

Thanks
Dib Urim