KnowledgeBase 00027: File System Performance on Windows

Last updated: 17 Feb 2017 Applies to: All versions

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The Problem

Windows systems allocate memory in a manner that can prevent QM making best use of unused space to cache disk blocks. The effect on application performance can be massive. For example, a test program that writes 500,000 records, each about 250 bytes in size, with sequentially numbered record ids took over 20 minutes on a 1Gb system with the default Windows XP performance settings but only 23 seconds with the change described below.

Beware that changing Windows memory performance options to benefit QM may have a detrimental effect on the performance of other software. The best approach is to try it and decide which setting works best in your particular situation.

Windows XP and Close Relatives

To find the relevant performance option:

• Right click on the My Computer icon and select Properties.
• Select the Advanced tab.
• Click on the Settings button in the Performance box.
• Select the Advanced tab.

Selecting "System cache" from the Memory usage box will allow QM to make best use of available memory.

Windows Vista and Windows 7

Nothing is easy!

• Click on the Start button.
• Go to All Programs.
• Go to Accessories.
• Right click on Command Prompt.
• Click on Run as administrator.
• In the command prompt window, type fsutil behavior set memoryusage 2
• Reboot the system.

If you decide to revert to the default setting, repeat the above sequence but set memory usage mode 1.

Group Size

Choosing a group size that matches the underlying operating system page size may also be beneficial. In Windows systems, this is 4kb.

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