Tips:
Make absolutely sure you use a map that uses nodraw and other culling methods.
GM_Mobenix comes to mind. Though it's been a while since I researched, there may be other good ones designed now.
That will help a bit...prevents the server from having to send all player information to every player at the same time.
Only the player(s) in the same area are sent.
Bandwidth:
You're going to need ALOT.
The below was found on a steampowered forum, and was meant for DM/CS matches on tight maps.
Gmod is a bandwidth hog due to all the physics involved, AND the fact that most maps draw all players to each other. (See previous tip)
// TIP for setting your rates. This tip is coming from a thread in www.steampowered.com forum. We can't guarantee if it really works.
// In case of LAG issue you can change the following lines.
//
// Maximum amount of bandwidth clients can use (0=unlimited, max=20000)
// Formula : sv_maxrate = bandwidth X 125 / number_of_slots
// Example :
// Assumptions :
// . upload bandwidth = 768 kbps and download = 10mbps. Take the lowest value (768).
// . slots = 10
// So : sv_maxrate = 768 * 125 / 10 = 9600
// Minimum amount of bandwidth clients can use (0=unlimited, 4000=good to keep dialup gamers off the server)
// Example : we want unlimited
// sv_minrate 0
//
// Maximum updates per second that the server will allow. Increasing this value will take more cpu power, 100 is max.
// Formula : sv_maxupdaterate = sv_maxrate / 300
// Example : with same assumptions than above.
// sv_maxupdaterate = 9600 / 300 = 32
CPU horsepower:
Well, I've never done research, but know that my dual-core Opteron 2.8ghzx1mb cache, I can spawn 250 barrels and blow them up before getting a little lag.
What does this have to do with actual numbers... no idea, but, your server will be having to calculate physics for all players no matter what map it uses.
You're going to need no less than a dual, probably a quad core 2.2ghz or better, dedicated.
If your host shares with other servers on a box like that...uh, good luck.
Good luck.
