Compaq ProLiant 6000 Software Manual page 20

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