Microsoft KB Archive/929240

= FIX: I/O requests that are generated by the checkpoint process may cause I/O bottlenecks if the I/O subsystem is not fast enough to sustain the IO requests in SQL Server 2005 =

Article ID: 929240

Article Last Modified on 11/20/2007

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APPLIES TO


 * Microsoft SQL Server 2005 Developer Edition
 * Microsoft SQL Server 2005 Enterprise Edition
 * Microsoft SQL Server 2005 Enterprise Edition for Itanium-based Systems
 * Microsoft SQL Server 2005 Enterprise X64 Edition
 * Microsoft SQL Server 2005 Standard Edition
 * Microsoft SQL Server 2005 Standard X64 Edition

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Bug: #50000708 (SQL Hotfix)



Notice
Microsoft distributes Microsoft SQL Server 2005 fixes as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2005 fix release.



SUMMARY
This article describes the following about this hotfix release:
 * The issues that are fixed by this hotfix package
 * The prerequisites for applying the hotfix package
 * Information about whether you must restart the computer after you apply the hotfix package
 * Information about whether the hotfix package is replaced by any other hotfix package
 * Information about whether you must make any registry changes after you apply the hotfix package
 * The files that are contained in the hotfix package



SYMPTOMS
In SQL Server 2005, the checkpoint process may generate periodic I/O spikes. If the I/O subsystem is not fast enough to sustain the I/O requests, I/O requests may cause I/O bottlenecks when the checkpoint process runs.



CAUSE
This problem occurs because the SQL Server checkpoint process posts as many I/O requests as possible when it determines that it must flush dirty buffers based on the recovery interval. This behavior is by default.



RESOLUTION
A supported hotfix is now available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Prerequisites
To apply this hotfix, you must have Microsoft SQL Server 2005 Service Pack 1 (SP1) installed.

For more information about how to obtain SQL Server 2005 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

913089 How to obtain the latest service pack for SQL Server 2005

Restart information
You do not have to restart the computer after you apply the hotfix.

Registry information
You do not have to change the registry.

Hotfix file information
This hotfix contains only those files that are required to correct the issues that this article lists. This hotfix may not contain of all the files that you must have to fully update a product to the latest build.

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

SQL Server 2005, Itanium architecture version


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates



MORE INFORMATION
To use this hotfix to limit the number of checkpoint I/O requests per second, you must use the -k  startup parameter in SQL Server 2005. In this startup parameter,  represents the checkpoint speed in MB per second.

Note By default, the checkpoint process makes sure that SQL Server can recover databases within the recovery interval that you specify. If you enable this hotfix, the default behavior changes. Therefore, you may experience a long recovery time if you specify a very low value for the parameter. Additionally, backups may take a slightly longer time to finish because a checkpoint process that a backup initiates is also delayed. We recommend that you use the following methods to help eliminate an I/O bottleneck:
 * Have enough hardware to sustain I/O requests that are posted by SQL Server.
 * Perform sufficient application tuning.

If you do have to enable this hotfix, make sure that you perform enough testing before you apply this hotfix on production servers.

To configure SQL Server 2005 to use the -k  startup parameter, follow these steps
 * 1) Start SQL Server Configuration Manager.
 * 2) In SQL Server Configuration Manager, click SQL Server 2005 Services, right-click the instance of SQL Server 2005, and then click Properties. For example, right-click SQL Server (MSSQLSERVER).
 * 3) In the SQL Server (MSSQLSERVER) Properties dialog box, click Advanced, and then click Startup Parameters.
 * 4) At the end of the existing text, type ;-k in the Value column, and then click OK.

For example, if you want to throttle a checkpoint process to generate only 3 MB of I/O requests per second, use a startup parameter of –k3. When you do this, the checkpoint process calculates intervals automatically to keep the I/O requests within 3 MB per second.
 * 1) Restart SQL Server for the parameters to take effect.

This hotfix is also included in the cumulative update package (build 3161) for SQL Server 2005 Service Pack 2. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

935356 Cumulative update package (build 3161) for SQL Server 2005 Service Pack 2 is available

Keywords: kbqfe kbpubtypekc kbhotfixserver kbsql2005engine KB929240

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