First of all, I'd say that 2K per second is _not_ a lot of data. If your program is not keeping up with the input streams, post your code, and I'm sure we can figure out what's holding it up.

Also, I think that most logging systems will flush at the end of each line since the purpose of a logging module is to save the log message to permanent storage especially in the event that the program crashes shortly afterwards. Still, flushing should not significantly slow your program down. Again, if it is, show us what your code is like, and we can suggest how to improve it.