Microsoft KB Archive/839687

= Microsoft support policy on the use of network-attached storage devices with Exchange Server 2003 =

Article ID: 839687

Article Last Modified on 10/25/2007

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APPLIES TO


 * Microsoft Exchange Server 2003 Enterprise Edition
 * Microsoft Exchange Server 2003 Standard Edition

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For a Microsoft Exchange 2000 Server version of this article, see 317173.



For a Microsoft Exchange Server 5.5 version of this article, see 317172.



SUMMARY
''A network-attached storage system is a file-based storage system that can be attached to a Microsoft Exchange Server 2003 computer through the network redirector by using a file sharing protocol such as server message block (SMB), Common Internet File System (CIFS), or network file system (NFS). Exchange 2003 addresses a number of issues that prevent earlier versions of Exchange from being used in conjunction with network-attached storage devices. With these changes you can host Exchange 2003 database files on network-attached storage devices, but any solutions that provide this capability must also provide additional functionality to fully enable the solution. This includes manually moving the Exchange database files to the device, because the Exchange 2003 System Manager tool does not support moving database files to a remote file system.''



INTRODUCTION
This article discusses the Microsoft support policy on the use of network-attached storage devices with Microsoft Exchange 2003. Additionally, this article describes other issues that you must consider when you use Exchange 2003 with a network-attached storage device.



MORE INFORMATION
The following sections describe the Microsoft support policy on the use of various storage devices with Exchange 2003.

Network-attached storage devices that are qualified to display the &quot;Designed for Windows&quot; logo
Microsoft only supports the use of Microsoft Windows Hardware Quality Labs (WHQL) qualified storage devices with Exchange 2003.

Network-attached storage devices that are not qualified to display the &quot;Designed for Windows&quot; logo
Microsoft does not support the use of non-WHQL qualified storage devices with Exchange 2003.

Block storage devices that are qualified to display the &quot;Designed for Windows&quot; logo
Microsoft only supports the use of WHQL qualified storage devices with Exchange 2003.

Block storage devices that are not qualified to display the &quot;Designed for Windows&quot; logo
Microsoft does not support the use of non-WHQL qualified storage devices with Exchange 2003.

Additional issues to consider
You must consider the following issues when you select a disk system and disk access technology for use with Exchange 2003.

Performance
Exchange 2003, like other enterprise messaging systems, may add an extremely large load on the disk input/output (I/O) subsystem. In most large database programs, physical I/O configuration and tuning play a significant role in overall system performance. There are three major I/O performance factors to consider:
 * I/O bandwidth: The aggregate bandwidth, typically measured in megabytes per second, that can be sustained to a database device.
 * I/O latency: The latency, typically measured in milliseconds, between a request for I/O by the database system and the point where the I/O request is completed.
 * CPU cost: The host CPU cost, typically measured in CPU microseconds, for the database system to complete a single I/O operation.

Any one of these I/O factors may become a bottleneck, and all these factors must be considered when you design an I/O system for a database program.

If disk I/O is processed through the client network stack, the I/O is subject to the bandwidth limitations of the network itself. Even if you have sufficient overall bandwidth, you may experience greater latency and increased processing demands on the CPU than you experience when you use locally attached storage. Additionally, consider the availability of the network-attached storage when you plan an Exchange deployment where the storage is attached by using a network. Microsoft recommends that you help protect the Exchange computer, the storage system, and the connecting network by using an uninterruptible power supply (UPS).

Additionally, Microsoft recommends that you contact your storage vendor to obtain assurance that the end-to-end solution is designed for use with Exchange 2003 before you deploy any storage solution for Exchange 2003 databases. Many vendors have &quot;best practices&quot; guides for Exchange 2003.

Microsoft also recommends that you perform a benchmark of your I/O performance to make sure that none of the I/O factors that are described in this article cause a system bottleneck.

Reliability
Exchange 2003 uses a transaction log and associated recovery logic to help make sure that the database remains consistent if a system failure occurs or if an unmanaged shutdown event occurs. When the database manager writes to its transaction logs, the database manager must depend on the return of a successful completion code from the operating system as a guarantee that the data has been written to the disk and not just to a volatile cache that will be lost if a system failure occurs.

Additionally, the limits of recoverability are determined by the ability of the disk system to make sure that data that is written to the disk is stored and retrieved reliably. Microsoft recommends that you use disk systems that can detect imminent failures and that can salvage or relocate affected data.

Microsoft works with other vendors to identify and to resolve problems that affect the integrity and the recoverability of Exchange 2003 data. Exchange 2003 includes several internal mechanisms to detect and to isolate file-level damage to an Exchange 2003 database. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

314917 Understanding and analyzing -1018, -1019, and -1022 Exchange database errors

Clustering
Microsoft recommends that you make sure that the storage systems that you use to store Exchange 2003 data on clustered servers are qualified for cluster implementations, and that they are designed to support Exchange 2003 data. A storage system that performs well with Exchange 2003 in a non-clustered environment might not be suitable for use in a clustered environment. To obtain support for clustered configurations, the whole cluster must be listed on the Cluster Hardware Compatibility List (HCL).

Exchange 2003 requires messaging databases to be stored on storage volumes that are recognized by and that are registered with the Microsoft Cluster service Cluster Administrator tool.

Supportability
If you use Exchange 2003 incorrectly with a network-attached storage product, you may experience data loss, including a total loss of the Exchange database files.

Because of this, Microsoft recommends that you contact your storage vendor to obtain assurance that the end-to-end solution is designed for use with Exchange 2003 before you deploy any storage solution for Exchange 2003 databases.

Additional query words: XADM NAS

Keywords: kbclustering kbdiskmemory kbhardware kbfilesystems kbinfo KB839687

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