I’m sad to say that there is no exact way to determine this for a particular environment because there are so many variables.
It depends on the server memory, numer of processor, speed of file I/O, the platform (Widows/UNIX), the average message volume, the average message size and many other things.
The best thing to do is have a TEST environment that closely matches your production environment and do some load testing.
One suggestion I can make is that you don’t want to get in a situation where your recovery database contains more than a few hundred messages at any given time. Cloverleaf’s performance degrades VERY quickly as the recovery database begins to fill up with messages. Having your storage on some very fast disk drives, will help this quite a bit.
Our environment is on UNIX AIX5.3, 8g RAM, 4 processors and we run upwards of 50 threads and 15-20 processes in a single site with no performance issues.
My former company had a huge Solaris server with 32g RAM, 12 processors and they also had sites that contained 50-100 threads and 15-20 processes each, however, the number of sites was much larger and the message volume was about 2million per day for all sites/threads.