Microsoft KB Archive/314695

= Mirrored Drives Larger Than 137 GB Perform Slowly =

Article ID: 314695

Article Last Modified on 1/31/2007

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APPLIES TO


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

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This article was previously published under Q314695



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
Using 48-bit Logical Block Addressing (LBA) support (per ATA/ATAPI-6) permits hard disks to be larger than 137 gigabytes (GB) in size. When 48-bit LBA support is turned on for ATA Packet Interface (ATAPI) drives in a RAID 1 (mirroring) configuration, performance is noticeably reduced.

Note that if you install the update that is described in this article, you must add a registry value to turn on the LBA support. See the &quot;More Information&quot; section in this article for more information.



RESOLUTION
To resolve this problem, obtain the latest service pack for 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

The English version of this fix should have the following file attributes or later:   Date         Time   Version        Size    File name 17-Dec-2001 13:09  5.0.2195.4776  86,704  Atapi.sys



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 Windows 2000 Service Pack 3.



MORE INFORMATION
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Follow these steps:  Locate and then click the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\parameters

 On the Edit menu, point to New, and then click DWORD. Type EnableBigLba, and then press ENTER. On the Edit menu, click Modify. Type 1, and then click OK.</li></ol>

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

For additional information about how to install multiple hotfixes with only one reboot, click the article number below to view the article in the Microsoft Knowledge Base:

296861 Use QChain.exe to Install Multiple Hotfixes with One Reboot

Additional query words: kbBaseOS

Keywords: kbbug kbfix kbwin2000presp3fix kbqfe kbwin2000sp3fix kboswin2000fix kbhotfixserver KB314695

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