Operating on huge files will always cause the kind of problems you describe. Why? Because when you run the cp (or dd or what- ever) command, the OS takes and starts loading that file into cache, while writing it out to the destination. So what? The Last In, First Out algorithm used to determine what stays in RAM and what goes in swap sees this brand new file being used right *now*, and sees that Tomcat and Eclipse are *not* being used now. So, they get pushed aside, to make room for the file that *is* being used now.
Actually, the algorithm used most commonly now is Least Recently Used. There is a distinction in that newer memory pages may get swapped out if it has been longer since they were accessed.
Unfortunately, that one file takes up all of cache. So, the next time that you want to use Mozilla or Eclipse or whatever, it has to be taken back out of swap, and put back in RAM.
In this case, though, the difference is not apparent. The result is still as you describe.
-Roberto Sanchez
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