Windows - Slow to Format a New Disk

How to fix slow virtual disk formatting in Windows Server 2012 and later by temporarily disabling SCSI TRIM and Unmap commands using fsutil.

Windows Server 2012 (and later) hosts will, by default, issue SCSI TRIM and Unmap commands equivalent to the entire size of the virtual disk. This behavior is the same even if the "Perform a quick format" option is checked, which significantly slows down the format process.

It is possible to disable the SCSI TRIM and Unmap feature on the host for the duration of the format.

To Disable TRIM and Unmap

Using a Windows CMD window on the host, issue the following command:

fsutil behavior set DisableDeleteNotify 1

To Re-enable the Feature

Use the following command to re-enable the Trim and Unmap feature:

fsutil behavior set DisableDeleteNotify 0

To Verify the Current Setting

You can verify the current Trim and Unmap setting by issuing the following command:

fsutil behavior query DisableDeleteNotify

The output will show one of the following:

• DisableDeleteNotify=0 - The 'Trim and Unmap' feature is on (enabled).
• DisableDeleteNotify=1 - The 'Trim and Unmap' feature is off (disabled).

Affected Versions

• Only Windows Server 2012 and later hosts are affected. All earlier versions (e.g., Windows 2008) do not exhibit the same issue.

Non-server Versions

• Non-server versions of Windows (e.g., Windows 8.x and 10.x) do not support the DisableDeleteNotify parameter.

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Document Information

• Last Updated: 2024-08-29
• VergeOS Version: 4.12.6