How to determine the appropriate page file size for 64-bit versions of Windows Server 2008 and or Windows 2008 R2
The 64-bit versions of Microsoft Windows Server 2008 and Microsoft Windows Server 2008 R2 can support more RAM than the 32-bit versions of Windows Server. 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.
For more information see: http://support.microsoft.com/kb/2021748/en-us?sd=rss&spid=12925