server problems

[teapotboy]

I run my own tekkit classic server and play with a friend on it but, after 5 minutes of playing it starts to lag my game but not my friends. its definitly not my computer not being good enough to run it because its fine on single player. please help.

[weirleader]

But if you're running a server plus the game then you're potentially doubling the RAM used.  Check RAM usage when it starts to lag and post here both how much each is using and how much total you have.  One process will be 'java.exe' and the other will be 'javaw.exe'.