What’s the issue?
Instant File Initialization (IFI) is a Windows feature that allows SQL Server to skip zeroing out newly allocated space in data files. Without IFI, whenever SQL Server creates a new database, grows a data file, or restores a database, Windows must write zeros across every byte of the new space before it can be used.IFI is granted by assigning the “Perform Volume Maintenance Tasks” privilege to the SQL Server service account. Starting with SQL Server 2016, the installer offers to enable this during setup, but it can be missed or left unchecked.
Why is this a problem?
Without IFI, data file growth and database restore operations can take dramatically longer, sometimes by orders of magnitude. A restore that should complete in minutes may take hours, and autogrowth events that should finish in milliseconds can stall the database long enough to cause query timeouts and application errors. In a disaster recovery scenario, the extra time required to restore large databases directly extends your downtime.Note that IFI applies only to data files; log files must always be zeroed out for transactional integrity reasons, so this setting does not affect log growth.
What should you do about this?
Verify the current status by running SELECT instant_file_initialization_enabled FROM sys.dm_server_services WHERE servicename LIKE ‘SQL Server%’;. A value of Y indicates IFI is active. To enable it, grant the “Perform Volume Maintenance Tasks” user right to the SQL Server service account through the Local Security Policy editor (secpol.msc) under Local Policies > User Rights Assignment, or via Group Policy in domain environments. Restart the SQL Server service for the change to take effect, then verify again using the query above.If the service account changes in the future, remember that the privilege must be granted to the new account, so include this step in your service account change procedures.