How many rsync over ssh simultaneous backups?

[Gian G. Spicuzza]

Hello,

     I am trying to estimate the number of users I can hold on my rsync 
backup server if all users are connecting at about the same time.  I am 
using rsync over ssh with 256bit-aes encryption.  Here are my average 
server specs (from least powerful to most powerful):

2.8GHz P4
1GB Ram
1TB SATA w/ RAID 10 for 500GB usable space
Kernel 2.4.32 with PaX-Enabled (causes moderate preformance decrease).

hdparm shows:

cache reads at 932 MB/sec
buffered reads at 50 MB/sec

-----
3GHz P4 w/ 1MB cache
2GB Ram
1.5TB SATA w/ RAID 10 for 750GB usable space
Kernel 2.4.32 with PaX-Enabled (causes moderate preformance decrease).

hdparm shows:

cache reads at 2,080 MB/sec
buffered reads at 107 MB/sec

All other servers specs are between the two above.

Most clients are uploading <100MB of data @ 320kbps (at max 40KB/s)
Few clients will keep longer connections uploading more, but a majority 
only sync under 100MB.

Thank you for any help, I appreciate it!

--Gian G. Spicuzza