The Cache performance object consists of counters that monitor the file system cache, an area of physical memory that stores ...

The Cache performance object  consists of counters that monitor the file system cache, an area of physical memory that stores recently used data as long as possible to permit access to the data without having to read from the disk.  Because applications typically use the cache, the cache is monitored as an indicator of application I/O operations.  When memory is plentiful, the cache can grow, but when memory is scarce, the cache can become too small to be effective.