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Wednesday, February 16, 2011

Enable or Disable Write-Caching- Windows 7




How to Enable or Disable Write-Caching for a Storage Device in Windows 7

Information
Write caching in a connected storage device refers to the use of high-speed volatile memory to collect write commands sent to data storage devices and cache them until the slower storage media (either physical hard disks or low cost flash memory) can accommodate them. Most devices that use write caching require that power be supplied continuously.



This article will show you how to enable write caching to have better performance for a storage device, or disable write caching for quick removal of a storage device without having to use Safely Remove Hardware.

Tip
If high data transfer performance is your main concern, you should enable both of these settings in OPTION TWO below:
In the Removal Policy section, select the Better Performance option.
In the Write-caching policy section, select Enable write caching on the device (if the system hardware and storage device support these features).

Warning
You must be logged into a administrator account to be able to do this tutorial.

OPTION ONE

Disable Write Caching for Quick Removal

Note
This option is usually the best choice for storage devices that you are likely to remove from the system frequently, such as USB flash drives, SD, MMC, Compact Flash, or similar memory cards, and other similar externally attached storage devices.

When you select the Quick Removal option, Windows 7 manages commands sent to the device using a method called write-through caching. In write-through caching, the device operates on write commands as if there were no cache. The cache may still provide a small performance benefit, but the emphasis is on treating the data as safely as possible by getting the commands to the storage device. The main benefit is that you can remove the storage device from the system quickly without risking data loss. For example, if a flash drive were to be accidentally pulled out of its port, the data being written to it is much less likely to be lost.

1. Open the Control Panel (All Items view), and click on the Device Manager icon.

2. In Device Manger, double click on Disk drives to expand it, then double click on the listed storage device that you want to disable write caching for. (See screenshot below)



3. Click on the Polices tab. Under the upper Removal policy section, select (dot) Quick removal, or check the Turn off Windows write-cache buffer flushing on the device box, and click on OK. (See screenshot below)





4. Click on Yes to restart the computer to apply. (See screenshot below)

WARNING:
This will restart the computer immediately. You should save and close anything else that you are working on first.

 
OPTION TWO

Enable Write Caching for Better Performance


Note
This option is usually the best choice for storage devices that must provide the highest possible performance and that you intend to not remove from the system frequently, such as internal hard disk drives. If you choose this option and the device is disconnected from the system before all of the data is written to it (such as if you remove a USB flash drive), you could lose data. When using this option for a storage device (ex: USB flash drive), you must use Safely Remove Hardware to disconnect the device safely to prevent possible data loss.

When you select the Better Performance option, Windows 7 uses a method known as write-back caching. In this method, the storage device itself is allowed to determine whether using the high-speed cache will save time completing the write commands. If it will, the device signals to the computer that the data has been stored successfully even though the data may not actually be present in the storage device yet (such as the hard disk or flash memory). This method markedly increases the throughput of storage operations, which are often a major bottleneck for system performance overall. However, if the power supplied to the device (ex: external hard drive) fails for any reason, any data still in the cache (that the computer system believes is safely stored) could be lost.

By default, Windows 7 uses cache flushing. This means that the system will periodically instruct the storage device to write all data waiting in the cache to the storage device. When you select Enable write caching on this device, you turn can turn off these periodic commands to transfer the data. Not all devices support all of these features.

1. Open the Control Panel (All Items view), and click on the Device Manager icon.

2. In Device Manger, double click on Disk drives to expand it, then double click on the listed storage device that you want to enable write caching for. (See screenshot below)



3. Click on the Polices tab. Under the upper Removal policy section, select (dot) Better performance. (See screenshots below)

NOTE:  
By default, Enable write caching on the device is also checked. If not, then check it as well.




4. To Turn Off Windows Write-cache Buffer Flushing on the Device -

WARNING:
To Prevent data loss. Do not check this option unless the storage device has a separate power supply that allows the device to flush it's buffer in case of a power failure.

A) Select (check) the Turn off Windows write-cache buffer flushing on the device box. (See screenshots above)

5. Click on OK. (See screenshot below step 3)

6. Click on Yes to restart the computer to apply. (See screenshot below)

WARNING:
This will restart the computer immediately. You should save and close anything else that you are working on first.


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