Detecting Memory Bottlenecks
The best indicator of a memory bottleneck on Exchange servers is the rate of hard page faults. Hard page faults occur when the application cannot find data that it needs in memory and must access the disk subsystem to retrieve it. This slows down the Exchange server because the data must be taken from the disk subsystem, a process that is slower than retrieving the data from memory. Accessing the data from the disk subsystem also increases the load on the disk subsystem.
This is why adding more memory to the Exchange server can solve some disk subsystem bottlenecks that affect performance. Examine the following Windows 2000 Performance Monitor counter to determine whether the Exchange server's memory is forming a bottleneck:
Overview counter-Memory: Pages/SecThe Pages/Sec counter reports the number of pages read or written to a disk to resolve page faults. You can turn this on when your system is under a typical load. If this counter averages greater than 5, a memory bottleneck is starting to form, and your disk subsystem is beginning to take a beating.