Instant file initialization is a Windows security policy that allows processes to forgo the step in which the operating system zeroes-out the file when allocating disk space to a requesting process. This can benefit SQL Server during database data file creation and during activities such as restoring a backup or auto-growing data files. These actions can request large chunks of physical disk space from the OS. Allowing this space to be made available instantly to SQL Server can result in better performance in these cases.
To enable this option, ensure the Perform Volume Maintenance Tasks security policy is granted to the appropriate user (the account running the SQL Server service). Windows Administrators should have this right by default.
Special security considerations should be taken into account when this feature is enabled because the allocated disk space is not overwritten until the requesting process writes to the file. SQL Server mitigates the risk while the data files are still attached by utilizing a discretionary access control list (DACL) that only allows certain users to access files initialized in this manner.