Warning If you turn on the
Power Protected write cache option for a write-caching disk drive, you turn off routines that are built in to the Windows 2000 disk drivers that make sure that critical data is written to the disk immediately, instead of being written to the disk later from the disk's built-in write cache. Do not turn on the
Power Protected write cache option unless your computer and any
connected hard disks are protected against accidental or inadvertent power
loss through hardware design that may include such features as redundant battery-backed power supplies or onboard batteries on caching controllers. Contact the vendors of your computer and storage devices to determine the degree of protection afforded by your hardware. Do not turn on the
Power Protected write cache option unless you understand and accept the level of risk that may be involved, and are confident that this risk has been mitigated through appropriate hardware power protection.
For more information about this issue, click the following article number to view the article in the Microsoft Knowledge Base:
281672
Possible data loss after you enable the "Write Cache Enabled" feature
Note In Windows XP, the Power Protect mode is not displayed in the output of the Dskcache.exe tool.
A supported feature that modifies the default behavior of the product is available from Microsoft. However, this feature is intended to modify only the behavior that this article describes. Apply this feature only to systems that specifically require it. This feature might receive additional testing. Therefore, if the system is not severely affected by the lack of this feature, we recommend that you wait for the next software update that contains this feature.
If the feature is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the feature.
Note If additional issues occur or if 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 feature. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
Note The "Hotfix download available" form displays the languages for which the feature is available. If you do not see your language, it is because the feature is not available for that language.
The 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
-------------------------------------------------
24-Feb-2003 20:19 1.0.0.0 10,512 Dskcache.exe
Dskcache.exe Usage Information
dskcache [ +p | -p ] [ +w | -w ] [/i | /s | Drive_Specifier ]
- Set (+) or clear (-) the disk cache value:
- p : Power protected write cache (not supported on all operating system
versions)
- w : Write cache
- Drive selection (default is all drives)
- /i : Integrated device electronics (IDE) disks only
- /s : Small computer system interface (SCSI) (includes Fiber Channel) disks only
- Drive_Specifier : Drive letter, volume name, or physical drive. Use the following formats:
- If no options are used, current settings for all fixed disks
will be displayed.
Notes- Use the w switch to turn on and turn off
write caching to improve disk performance.
- Use the p switch to turn on and turn off
the
Power Protected write cache option.
If you turn on the
Power Protected write cache
option, you increase the risk of data loss or corruption that may occur during a power outage or
equipment failure. Only turn on this option for disk devices that are adequately
protected against accidental loss of power. See the warning at the beginning of this section.
Note The
Power Protected write cache option can only be
turned on for disks that are currently present. Because the
Power Protected write
cache option is turned off by default, this option is turned off for any disks that
may be added after you apply this setting. If you add additional disks, you
must turn on the
Power Protected write cache option for those added disks for the setting to take effect.
Dskcache.exe Command Output
If you run Dskcache without any parameters, the current write cache settings for all hard disks are displayed. For each hard disk currently present on your computer, the following information is displayed:
Disk device:
Volume name of the form:
\\?\Volume{8fc37c41-bdd3-11d5-b897-806d6172696f}\
Current Settings:Write Cache is [ enabled | disabled ]
Power Protect is [ enabled | disabled ]
If you run Dskcache with the
w switch or the
p switch, the specified settings are applied to the specified disks immediately. This behavior occurs if the disks and their drivers support querying and modifying the requested configuration options. (See "Common Error Messages" below.)
For each fixed disk that is currently present on your computer, the following information is displayed:
Disk device:
Volume name of the form:
\\?\Volume{8fc37c41-bdd3-11d5-b897-806d6172696f}\
Current Settings:Write Cache is [ enabled | disabled ]
Power Protect is [ enabled | disabled ]
New Settings:Write Cache is [ enabled | disabled ]
Power Protect is [ enabled | disabled ]
Common Error Messages
You may receive one of the following error messages:
Error setting Write Cache value. (1) Incorrect function.
This error message indicates that the specified disk device (or its driver) does not support changes to its write cache status through the Microsoft-implemented driver commands (IOCTLs). Many RAID controllers are included in this category. For these disks, the write cache is not configurable through any means available from Microsoft. The write cache is configurable only through mechanisms that the hardware vendor provides. The Microsoft disk drivers do not enable write caching for such drives. Therefore, the Dskcache tool that is described in this article and the hotfix that is described in Microsoft Knowledge Base article 332023 KB.EN-US are not applicable in these cases.
Error getting Write Cache value.
(50) The write cache is not modifiable.
This error message indicates that the specified disk device (or its driver) does not report its write cache status through industry-standard mechanisms (that is, according to the relevant SCSI or ATAPI [IDE] specifications). Many RAID controllers are included in this category. For these disks, the write cache is not configurable through any means available from Microsoft; it is configurable only through mechanisms provided by the hardware vendor. The Microsoft disk drivers do not enable write caching for such drives. As a result, the Dskcache tool that is described in this article and the hotfix that is described in Microsoft Knowledge Base article 332023 KB.EN-US are not applicable in these cases.
Error getting Write Cache value.
(1117) The request could not be performed because of an I/O device error.
This error message indicates that the disk device does not return information about its write caching status in response to the appropriate SCSI or ATAPI command. This error message is simply an indication of the capabilities (or lack thereof) of the device or its driver, and it typically implies that either the device does not support write caching or that the device driver does not support the commands that are required to query and set the device's write cache setting.
To resolve this issue, contact the vendor of the disk device.
Error getting Power Protect value.
(21) The device is not ready.
This error can have several different causes. If this error occurs on only one disk, and the disk is part of an external storage array, this message may indicate that the disk is simply offline. Bring the disk online and repeat the
dskcache command to apply the settings you want to use. If this error occurs on all disks that are part of a storage array shared by multiple servers in a cluster, this message typically indicates that you are running the
dskcache command on a server (node) that is not the owner of the storage array or device.
To apply the
Power-Protected write cache setting to all servers in the cluster, follow these steps:
- Install the update from 332023 KB.EN-US on all nodes (servers) in the cluster, and then restart each server so that the updated drivers will be loaded.
- On each server in turn, make that server (node) the Owner of the disk or array (using Move Group to move the disk resources to that node), and then run the dskcache command on that server.
- Repeat step 2 as required for each server (node) in the cluster.