Compaq ProLiant 6000 Performance of Microsoft Exchange Server 5.0 on Compaq Pr - Page 16

WHITE PAPER (cont.) NOTE: READ I/O on the IS for Configuration A decreased at 3000 users due mainly to disk bottlenecks and architecture issues in Exchange Server. NOTE: The Log files do not incur READ activity during normal operations, only during recovery. CONTROLLER CACHING: Microsoft recommends turning off disk controller caching based on the assumption that common generic array controllers provide NO protection against data loss and corruption. The Compaq SMART-2 Array Controller, however, provides Error Checking and Correction (ECC) and battery backup for its cache. When a cache is amply protected, as in the case of the SMART-2, Compaq recommends enabling this cache for maximum performance benefit. ECG052.0897 1...6 Exchange Disk I/O Profile (Configuration A) I/Os per second 250 200 150 100 50 0 500 1000 1500 2000 User Load 2500 3000 Figure 6. Exchange Disk I/O Profile (Configuration A) Read I/Os - IS Write I/Os - IS Write I/Os - Log Disk I/Os per Second 250 200 150 100 50 0 500 Exchange Disk I/O Profile (Configuration B) 1000 1500 2000 User Load 2500 3000 Read I/Os - IS Write I/Os - IS Write I/Os - Log Figure 7. Exchange Disk I/O Profile (Configuration B) Here are some important points about disk subsystem capacity planning and sizing: • The benefit increases as the number of users increases. This is because the number of disk I/Os required also increases, so the benefit of the array controller becomes more apparent (compare Configuration A to Configuration B). • Since the Exchange Server IS Buffers manage database/disk READ caching, Compaq recommends setting the SMART-2 Array Controller cache to 100% WRITE. • The disk subsystem should be carefully designed in accordance with the I/O profile generated by the characterized workload.