A slow removable storage device may be very slow to respond when multiple read and write operations are performed against the device in Windows Server 2003 or in Windows XP x64 Edition

Consider the following scenario:

• You connect a relatively slow removable storage device to a Microsoft Windows Server 2003-based computer or to a Microsoft Windows x64-based computer. For example, this device might be a Magneto-Optical (MO) drive, a compact flash memory device, a USB 1.1 flash memory device, or some other similarly slow device.
• In Device Manager, you set the write cache policy to Optimize for performance on the Properties dialog box.
• You try to perform a disk operation against the device by using an application. Meanwhile, another application is simultaneously writing to the disk.

In this scenario, the operation may take a long time to finish.

This problem may occur if you are running Windows Server 2003 Service Pack 1, Windows XP x64 Edition, or the original Release to Manufacturing (RTM) version of Windows Server 2003, and if you have installed the hotfix installed that is described in the following Microsoft Knowledge Base article: The problem is caused by a bug in the Usbstor.sys driver. The hotfix that is described in this article modified the driver for these operating systems.

For more information about the updates that are included in Windows Server 2003 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. To work around this problem, use one of the following methods.

Method 1: Use the "Optimize for quick removal" write cache policy

Note If you are using SCSI or IDE disks, you cannot select the Optimize for quick removal option for the device. If you are using SCSI or IDE disks, you must use the Optimize for performance option.

To select the Optimize for quick removal option for the device, follow these steps:

1. Click Start, click Run, type devmgmt.msc, and then click OK.
2. Right-click the device, and then click Properties.
3. Click the Policies tab.
4. Click Optimize for quick removal, and then click OK.
5. Restart the computer.

Method 2: Modify the registry if you cannot use the "Optimize for quick removal" write cache policy

If you are using a SCSI or an IDE disk and cannot use the Optimize for quick removal option, follow these steps:

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click the following subkey in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\<XXX>\<YYY>\<ZZZ>\Device Parameters\Classpnp
   Note In this registry subkey, XXX, YYY, and ZZZ are the strings that represent the disk device that you are using.
   
   For example, a sample SCSI MO device might have a Classpnp subkey that is similar to the following:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\SCSI\Optical&Ven_XXXXX&Prod_YYYYY&Rev_0800\4&1faa839c&0&050\Device Parameters\Classpnp
   
   
   Note if the Classpnp subkey does not exist, you must create it. To do this, click Edit, point to New, and then click Key. Type Classpnp for the name of the subkey, and then press ENTER.
3. With the Classpnp subkey selected, click Edit, point to New, and then click DWORD Value.
4. Type UserRemovalPolicy for the DWORD name, and then press ENTER.
5. Right-click UserRemovalPolicy, and then click Modify.
6. In the Value data box, type 3, and then click OK.
7. Exit Registry Editor.
8. Restart the computer.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

In Windows XP or in Windows Server 2003, you can change the write cache policy to optimize write performance for a disk device and for data safety. You can select either the Optimize for quick removal option or the Optimize for performance option in Device Manager.
If the Optimize for performance option is selected, data that is written by an application is cached by the operation system, and lazy write is used for the cached data.

When a slow device, such as an MO drive or a compact flash memory device, writes data by using lazy write, and you simultaneously try to view files on the device by using an application or by viewing the device status in Device Manager, a delay may occur. You must wait until the lazy writing finishes.

Technical support for Windows x64 editions

Your hardware manufacturer provides technical support and assistance for Microsoft Windows x64 editions. Your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation with unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with your Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware.

For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site: For product information about Microsoft Windows Server 2003 x64 editions, visit the following Microsoft Web site: