maximum number of squid proxy connections

Solution 1:

It depends on the nature of the connections, the speed of the networks between the proxy and server / proxy and client. Knowing that there are 5000 users doesn't give a lot of information about the number of concurrent connections. But presumably these people are able to access the internet currently - so why not measure the what they are doing now?

Certainly for this volume it would be reasonable to provide more than one proxy in terms of reliability, and since licensing costs should not be an issue, then I'd recommend using more low-spec machines over fewer high-spec ones. I suspect that 2-3 very low end boxes (Athlon X2, 2-4Gb memory) but with extra HD capacity (say 2x500Gb disks as a mirrored array) would suffice. They'd also benefit from having a faster interconnect independent of the internet and intranet connections - so at least 3 NICs. Once you've worked out how to the load balancing, adding more nodes (if you need them) is trivial.

C.