Compaq ProLiant 6000 Performance of Microsoft Exchange Server 5.0 on Compaq Pr - Page 20

WHITE PAPER (cont.) NOTE: Remember that there is no benefit in tuning IS Buffers beyond 20,000 in Exchange Server 5.0. ECG052.0897 2...0 • The log volume must always be fault tolerant. Because of the sequential-WRITE-only nature of the log volume, having many disks in a RAID set does not provide a significant benefit. Two high-capacity disks mirrored (RAID 1) is a configuration that provides good sequentialWRITE performance and excellent fault tolerance. Note that the IS buffers will aid log volume performance. • SMART-2 controllers with WRITE cache should be set to 100% WRITE (using the Array Configuration Utility) for all volumes. The SMART-2/P and the SMART-2DH have 4 MB and 16 MB of cache, respectively, that can be configured for WRITE. The SMART-2SL comes with 6 MB of cache that can be configured only for READ. The nature of Exchange Server disk I/O is sequential WRITEs for the Log files and random READs and WRITEs for the IS database files (READ-to-WRITE Ratio = approximately 3:1). Since the IS Buffers account for disk READ caching, and this I/O is random and small in size (4K), there is no benefit in setting the SMART-2 cache for READ performance. Memory • 128 MB of RAM is an adequate amount of system memory to start with, up to the 1000-to1500-user range. 256 MB can provide additional benefit for user loads beyond 1500. • Adding memory beyond 256 MB will provide minimal performance or capacity benefits. • Monitor the available memory on the system using NT Performance Monitor. If there is unused memory available on a consistent basis, allocate a portion of it to the IS Buffers. However, do not over-allocate RAM. There should be at least 10-15 MB of free memory in the system at all times. • Increasing RAM in the system and allocating it to the IS Buffers can significantly improve client response time. In some cases, doing this may be more cost-effective than adding disks to the drive subsystem. General • Always run Exchange Optimizer after the initial setup of Exchange Server. Also, run it after changing configuration of the server. • Always ensure that your capacity planning simulations include proper workload characterization. Use the tools available to profile your actual messaging/GroupWare environment. These tools include STORSTAT, MAILSTORM, INETLOAD or other thirdparty tools. • Use resources such as field staff, tools, and white papers available from both Microsoft and Compaq to assist with capacity planning, performance optimization, and deployment of Compaq servers in an Exchange Server environment. • Be sure to consider whether a resource is a bottleneck before adding more of that resource. • Understand what measurement is important for the appropriate capacity planning exercise. For example, response time is the key indicator of performance for servers directly supporting users (for example, Mail and Public Folder servers), whereas throughput is the key measurement for servers indirectly supporting users (for example, Bridgehead, DS Replication, Free/Busy, and DL expansion servers).