Compaq ProLiant 6000 Performance of Microsoft Exchange Server 5.0 on Compaq Pr - Page 15

ECG052.0897 WHITE PAPER (cont.) 1...5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 500 Disk Queue Length (Hardware Configuration B) 1000 1500 2000 User Load 2500 3000 Exchange IS Exchange LOG OS/Pagef ile Figure 5. Exchange Disk Queue Length (Configuration B) Disk I/O Profiling An important technique in capacity and performance planning and analysis is I/O profiling. It is necessary to plan for the disk I/O capacity that your application will require in production. Once again, workload characterization is key to making this planning successful. With proper workload characterization and simulation, the I/O requirements for the disk subsystem can be observed, and the subsystem design can reflect those observations. Microsoft Exchange Server is, in a generic sense, a client/server transaction-based database application. As such, the disk I/O profile is much like that of a database engine such as Microsoft SQL Server. Microsoft Exchange Server stores data in two key files, PRIV.EDB and PUB.EDB, which hold private data (Mail) and public data (Public Folders). A third file, DIR.EDB stores Exchange Server directory information. Two additional areas of interest are Queues (IMC, MTA, etc.) and Log files. It is important to understand the types of disk I/O generated by access to each of these key data file areas in Microsoft Exchange Server. For the Exchange Server data files (PRIV, PUB, and DIR), the access patterns are random READ and WRITE (approximately 70% READ, 30% WRITE) in nature. For the Log files, the access patterns are sequential WRITE in nature. This information is key to designing your disk subsystem to deliver the I/O capacity required by the production user load. For example, understanding not only the volume of disk I/Os but also the type (READ or WRITE) is a requirement for making choices about RAID levels and number of drives (See Compaq White Paper Configuring Compaq RAID Technology for Database Servers).