XADM: Messages Are Backed Up in Message Transfer Agent and Internet Mail Service Queues to the Information Store (318178)

RESOLUTION

To resolve this problem, complete each of the following steps in the order that they are presented. After each step, test to see if the performance has improved. If it has not improved, continue to the next step.

1. Increase the number of log buffers for the information store.For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

   188676 XADM: Log Stalls/sec Are Regularly Greater Than 0 (Zero)

2. Run Performance Optimizer in verbose mode.For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

   246125 XADM: Exchange Server 5.5 Performance Optimizer Verbose Mode

3. Increase throughput between the MTA and the information store.For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

   234702 XGEN: MTA Queue to Information Store Processing Slowly

4. If the log files have a dedicated disk controller, which is a controller that only services disks that contain log files, configure the disk controller to use 50% write cache and 50% read cache. Continue to increase the write cache percentage until the problem is resolved. You may have to configure the disk controller for 100% write cache and 0% read cache.NOTE: During typical operation, Exchange Server does not perform read operations against the log files. As a result, the read cache provides little or no performance benefit. Contact your hardware vendor for more information about how to turn on and modify the disk controller write cache.
   
   WARNING: The disk controller must have an extremely reliable battery back up; otherwise, turning on the write cache may result in data loss. Microsoft does not recommend turning on the write cache on the physical disk under any circumstances because there is no battery back up for this cache to prevent data loss. Before you turn on the write cache on the controller, it is important to understand the inherent risks of this technology. It is possible for a hardware write cache to be safe for Exchange Server if the hardware manufacturer has included safety mechanisms that prevent the accidental removal of uncommitted cache data. For additional information, contact your hardware vendor. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

   188589 XADM: Exchange DB and Caching Hard Disks and Controllers

5. Log files should have a dedicated disk or disk set to avoid contention with other processes. For example, you should not put MTA or information store database files on the same disk set as the log files. This configuration would require the controller to split its time between the log files and the other files that are being written to disk.
6. For a fault tolerant solution with the best performance, store the information store log files on a hardware RAID 0+1 disk set (mirror set). A stripe set increases performance by dividing data into blocks and spreading them, in a fixed order, across all disks in the array. Because dual write operations in a mirror set can degrade system performance, Microsoft recommends that you use duplexing, which provides each mirror set with its own host adapter. The mirror set increases fault tolerance if a disk in one of the stripe sets fails. However, if the primary disk set in the mirror set fails, it might incur some downtime, and you would have to manually break the mirror set by using a disk editor. For additional information, contact your hardware vendor.
7. In Windows NT 4.0, run perfdisk -y at a command prompt to turn on physical disk counters. By default, physical disk counters are turned on in Windows 2000. If the counters have been turned off in Windows 2000, run perfdisk -yd to turn on the counters. Use Performance Monitor to determine if disk I/O is contributing to this problem. For additional information about monitoring disk performance, click the article number below to view the article in the Microsoft Knowledge Base:

   146005 Optimizing Windows NT for Performance

If none of these Exchange Server and disk tuning changes result in a significant improvement in performance, Microsoft recommends that you run the hardware diagnostics utilities that are provided by your hardware manufacturer. Microsoft also recommends that you periodically contact your hardware vendor for available firmware updates because many perceived hardware issues can be caused by firmware.