I have a pair of linux servers that act as backup servers for us using rsync. These servers only recieve rsync sessions, they never initiate them (via cron, script, etc.). The clients that are being backed up initiate the rsync session (they are Windows machines mostly) and the backups are performed from remote locations via SSH.

I'm wondering what the practical limitation is for simultaneous connections for these backup servers? The clients tend to initiate their sessions in waves and we've seen performance problems with multiple rsync sessions happening at the same time. Does anyone know what the maximum number of sessions that you should have simultaneously in theory? I know its dependent somewhat on the backup server's hardware, but all four of our backup servers are IBM x306 series with 1Gb of RAM and 3.5Ghz P4 processors....

As such their is no limit specified by RSYNC guys for maximum simultaneous connections.

I'm looking for what might be the expected limit. I'm running a pair of IBM x306 servers and need to get a rough idea of how many simultaneous rsync sessions might be too many so that I can possible judge the cluster size requirements.

Other rate-limiting options to consider:

How fast is / are your disk(s)?
Are they on the same cables / controllers?
What is your network bandwidth?

Write a script to test them by opening up a certain number of rsync connections in the script..