Article ID: 314695 - Last Review: January 31, 2007 - Revision: 3.3

Mirrored Drives Larger Than 137 GB Perform Slowly

View products that this article applies to.
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  (http://support.microsoft.com/kb/256986/EN-US/ ) Description of the Microsoft Windows Registry
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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 "More Information" section in this article for more information.
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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  (http://support.microsoft.com/kb/260910/EN-US/ ) 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

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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.
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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:
  1. Locate and then click the following key in the registry:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\parameters
  2. On the Edit menu, point to New, and then click DWORD.
  3. Type EnableBigLba, and then press ENTER.
  4. On the Edit menu, click Modify.
  5. Type 1, and then click OK.
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  (http://support.microsoft.com/kb/265173/EN-US/ ) 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  (http://support.microsoft.com/kb/296861/EN-US/ ) Use QChain.exe to Install Multiple Hotfixes with One Reboot
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APPLIES TO
  • Microsoft Windows 2000 Service Pack 1
  • Microsoft Windows 2000 Service Pack 2
  • Microsoft Windows 2000 Advanced Server
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Keywords: 
kbbug kbfix kbwin2000presp3fix kbqfe kbwin2000sp3fix kboswin2000fix kbhotfixserver KB314695
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