The Windows NT Cache Manager adjusts the size of the file system cache based on whether a computer is a workstation or a server, the amount of physical memory in the computer, and the applications and services the computer is supporting. In general, it is counterproductive to override the Cache Manager and manipulate the cache size directly. If the cache is too small to be effective, it is best to increase the amount of physical memory on the computer, or to redistribute memory-intensive applications to other servers.
The Performance Monitor Memory: Cache Size counter is a useful indicator of the size of the file system cache. Task Manager also displays the size of the file system cache in the File Cache field of its Performance tab.
You can use also use Performance Monitor or PerfLog to log the Memory: Cache Size counter. A log of cache size reveals how the size of the file system cache changes over time. Compare this data to a measure of general memory availability, such as data from the Memory: Available Bytes counter. In general, when memory is scarce, the system trims the cache and when memory is ample, the system enlarges the cache.
Note the points in the log when the cache is smallest. Keep track of how small the cache gets and how often the cache is small. Also, note how much system memory is available when the cache size is reduced. This data is useful when associating the size of the cache to its performance.