Microsoft KB Archive/289261

= Backup Takes Much Longer When PAE Is Enabled =

Article ID: 289261

Article Last Modified on 1/31/2007

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APPLIES TO


 * Microsoft Windows 2000 Service Pack 1
 * Microsoft Windows 2000 Service Pack 3
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Service Pack 1
 * Microsoft Windows 2000 Service Pack 2
 * Microsoft Windows 2000 Service Pack 3
 * Microsoft Windows 2000 Datacenter Server

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This article was previously published under Q289261



SYMPTOMS
When you finish a backup while you are using Ntbackup.exe, if you start the computer with the PAE switch enabled, the backup may take longer than expected to complete (up to or longer than 10 times longer than expected). If you start the computer without the PAE switch, the backup finishes as expected.



CAUSE
NTbackup must write to a tape by using a tape block size in powers of two. When the PAE switch is used, the   value is reduced by one to allow for one extra level of page translation. This behavior causes the block size to be an odd-numbered size. When NTbackup tries to read or write to a tape whose block size exceeds the   value multiplied by 4 kilobytes (KB) (MaximumPhysicalPages &#215; 4KB), NTBackup defaults to a 1024-byte block size. This smaller block size severely reduces read and write performance.

The block size is calculated by multiplying the value in   by PAGE_SIZE (4096). With a non-PAE Kernel, this is 16 X 4096 = 65536, and with the PAE kernel, it is 15 X 4096 = 61440, which is not a power of two. Because of this, RSM and Ntbackup both default to a 1KB block size when preparing or writing to a tape, which severly affects performance.



Service Pack Information
To resolve this problem, obtain the latest service pack for Microsoft Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack

Hotfix Information
A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows 2000 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The US English version of this fix has the file attributes (or later) 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 tool in Control Panel.   Date        Time     Version           Size   File name ---   8/20/2002   05:01p   5.0.2195.5988   10,928   Tape.sys NOTE: To view the version number, right-click the file in Windows Explorer, click Properties on the shortcut menu, and then click the Version tab.

NOTE: Before NTBackup can use the proper block size, you have to re-prepare the tape media by using Removable Storage Manager (RSM). As soon as it is prepared, the tape block size will be adjusted to the largest block size available while using the power of two.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Microsoft Windows 2000 Service Pack 4.



MORE INFORMATION
For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the article number below to view the article in the Microsoft Knowledge Base:

265173 The Datacenter Program and Windows 2000 Datacenter Server Product

Keywords: kbbug kbfix kbperformance kbwin2000presp4fix kbqfe kboswin2000fix kbbackup kbwin2ksp4fix kbhotfixserver KB289261

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