This article describes a change in the behavior of the format command in Windows Vista.

The format command behavior has changed in Windows Vista. By default in Windows Vista, the format command writes zeros to the whole disk when a full format is performed. In Windows XP and in earlier versions of the Windows operating system, the format command does not write zeros to the whole disk when a full format is performed.

The new format behavior may cause problems for the on-demand allocation modes that a volume storage provider, such as a Storage Area Network (SAN), supports. Problems may occur because the new format behavior prematurely triggers allocation of the backing space.

In the on-demand scenario, zeros do not have to be written to the whole disk because the volume storage provider initializes the on-demand-allocated data. To avoid causing unnecessary on-demand-allocation, you must use the quick format option.

You can use four methods to format a volume in Windows Vista. You can use the quick format option for these four methods:

•	Command line: Use the format /q command.
•	Diskpart: Use the format command together with the quick parameter. For more information, visit the following Microsoft Web site: http://technet2.microsoft.com/windowsserver2008/en/library/56863741-c5f3-4681-8667-2d566c8ddf231033.mspx?mfr=true (http://technet2.microsoft.com/windowsserver2008/en/library/56863741-c5f3-4681-8667-2d566c8ddf231033.mspx?mfr=true)
•	Windows Explorer: Click to select the Perform a quick format check box.
•	Disk Management (Diskmgmt.msc): Click to select the Perform a quick format check box.