Concepts and Planning << >>

Planning I/O Subsystem Needs

When planning your server's I/O subsystem, consider doing the following:

Adding more disk drives will help increase performance, especially if disk I/O is random in nature, as it is with the public and private information stores. All drives have mechanical limitations on performance, so adding more drives distributes the workload more efficiently.

After deciding on a storage solution, run the Performance Optimizer to evaluate the I/O subsystem and to recommend locations for relevant Microsoft Exchange Server files. If new disks are being added to a server, use the Performance Optimizer to experiment with I/O setup.

Partitioning Disks

To expand disk space, before installing Microsoft Exchange Server you can configure your disk for easy volume-set expansion. You should configure multiple physical disks into one virtual disk or striped set to host your Microsoft Exchange Server databases. Disk striping creates a virtual disk over two or more disks, which provides high capacity and high performance.

Hosting the page file on the same striped set as the databases improves I/O performance; this is important for servers low in memory.

If your computer has multiple disk drives, you may also want to consider other disk administration options (such as disk striping with parity and disk mirroring) to increase fault tolerance.

For more information, see your Windows NT Server documentation.

Disk Usage for Transaction Log Files

One of the most important performance considerations is whether to put the information store transaction log file on its own physical disk. Using a dedicated physical disk for files increases fault tolerance and system performance. The Performance Optimizer can be used to configure the directory transaction log files so that they reside on their own disk drive. Use the Windows NT file system (NTFS) format if the server will be backed up infrequently or if the size of the log files may grow to more than 2 gigabytes (GB).

Modifications to the directory database are usually infrequent, so putting the directory transaction logs on a separate drive isn't necessary. However, you can put the logs on servers used for large directory imports (running the directory synchronization component) or servers used primarily for large directory modifications.

If the Microsoft Exchange Server computer has only a few drives and a small amount of memory, and it can't support many users, you can put transaction log files and databases on the same striped set. However, the increased sensitivity to insufficient memory causes performance to decrease as the load on the server increases. When in doubt, dedicate a disk to the log files ¾ disks are cheaper than memory.

Disk Usage for the Information Store

In addition to planning disk space and usage for transaction log files, you should consider disk capacity for the information store. A server can have only one private and one public information store. The size of the information store grows as mailboxes, public folders, connectors, remote users, log files, and messages grow in numbers.

To improve performance, control the use of disk space by placing limits on the:

Later, you can adjust your available disk space by using the following strategies:

Choosing Caching Disk Controllers

Choose a server that has a caching disk controller with a high-speed bus interface, such as the Peripheral Component Interconnect (PCI) PC Card. These controllers provide optimal performance for Microsoft Exchange Server. Most of these controllers support hardware disk striping, which offers greater performance and less CPU use than Windows NT Server software striping.