Slow Network Performance After You Promote a Windows 2000-Based Server to a Domain Controller

If you upgrade a Windows 2000-based server to a domain controller, you may experience performance degradation on some hardware. For example, after the upgrade, network performance may be slower if you copy files to a share on a Windows 2000-based domain controller than if you copy the same files to a Windows 2000-based member server.

The following event ID message may be logged in the event log after you run the Dcpromo tool:

This problem may occur if a disk's write caching functionality has been turned off. If you use the Dcpromo tool to promote a Windows 2000-based server to a domain controller, the write caching functionality (write-back cache is a firmware function) is turned off for any of the logical drives that contain the Active Directory database or log files, including the system disk. Write caching is turned off because the File Replication Service (FRS) does not recover if power to the drive is interrupted and if critical updates are lost.

To prevent this problem from occurring, use a domain controller that has a file server to separate the system disk and the partitions where the Active Directory log file and database files are located from the data disks on which your file shares reside. Microsoft recommends that you place log files and database files on separate physical disks to improve performance and to help with data recovery.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Caching and Data Recovery

The cache is the area of RAM that contains data. When you write data to disk, the lazy-write technique in Windows 2000 indicates that the data is written; however, the data is still in the cache. Cache memory also exists on the disk controller (for example, small computer system interface [SCSI] controllers) or on the disk unit (for example, Enhanced integrated device electronics [EIDE] disks). Review the following information to decide whether you want to turn on the disk or controller cache:

• If you turn on write caching, disk performance improves, particularly if the disk is being heavily written to.
• Control of the write-back cache is a firmware function that is provided by the disk manufacturer. See the documentation supplied with the disk or disk controller. You cannot configure the write-back cache from Windows 2000.
• Write caching does not affect the reliability of the file system's own meta data. NTFS instructs the disk device driver to make sure that meta data writes get written regardless of whether write caching is turned on. Non-meta data is typically written to the disk, so this kind of data can be cached.
• Read caching in the disk has no effect on file system reliability.

On RAID 5 volumes and stripe sets, reading is faster than writing. Mirrored volumes also are typically faster at reading than writing, and are faster at writing than RAID 5 volumes.

For more information about Disk Tuning see the Server Operations Guide in the Windows 2000 Server Resource Kit.

For additional information about the write caching functionality, click the article numbers below to view the articles in the Microsoft Knowledge Base: For more information about possible causes of slow performance on Windows 2000 domain controllers that operate with Windows XP client computers, click the following article numbers to view the articles in the Microsoft Knowledge Base: