The 64-bit versions of Windows Server 2008 and Windows Server 2008 R2 can support more RAM than the 32-bit versions of these products. When lots of memory is added to a computer, a paging file may not be required. When you use the Memory-Pages/sec counter to measure paging file use, the value that is returned may not be accurate. To obtain an accurate measurement of paging file use, you must also use other performance counters. You can use System Monitor measurements to calculate the size of the paging file that your computer requires.
Windows Server 2008 and Windows Server 2008 R2 domain controllers and DFS replication, certificate, and ADAM/LDS servers are not supported without a configured paging file (also known as a page file). Because the algorithm of the LSASS database cache depends on the "transition pages repurposed/second" performance monitor counter, a page file is required to make sure that the database cache can release memory if memory is requested by other services or applications.