Adaptec 2120 performance very poor - What now?

[Matt Hartzell]

I am experiencing very poor performance on an Adaptec 2120, and I can 
see that (now) the 2120 is not a good choice for a highly used ftp server.

Now that I have about 500G of data stored on it I really can't back it 
up and rebuild it using some other controller.

I know the 2200 can be swapped out for the 2120 with out rebuilding the 
array, but in my testing the 2200 is just as poor when witting to 
reading / writing to the same channel.

What other products would provide faster performance under FreeBSD AND 
support a seamless (no rebuild/reinstall/restore) migration?

Thanks in advance for any and all help.