A number of our servers run Windows 2008r2 and look after huge data areas containing hundreds of millions of files.
We were finding no matter how much memory we gave the servers, after a week or so, the memory usage would be between 90 and 100% full. Our only fix at the time was to restart the server each time to free up the memory. There was no application taking this memory, it was just disappearing.
A very good friend of mine had come across this problem before and suggested using SetSystemFileCacheSize64.exe which clears the system cache and frees up the memory instantly. The problem was related to the amount of files Windows was keeping in it’s cache.
You can also set SetSystemFileCacheSize64.exe to limit the amount of cache the system uses.
I hope this may help others who have the same problem.