Occurs while waiting for non-data-file disk I/O to complete. For example while growing a transaction log disk I/O is required to zero-out the file. Backup and restore operations can also accumulate this wait counter. As this wait accumulates during backups moderate values are expected

Resolved by


Suggested solutions

  1. Use backup compression if available
  2. Remove any unused indexes (less data to backup)
  3. Upgrade backup disk
  4. Preallocate data files
  5. Increase the auto-growth from the default (less frequent growths)
  6. Investigate disk performance

Additional research

SQL Server Database Growth and Auto Growth Settings
A cause of high-duration ASYNC_IO_COMPLETION waits

See more

Consider using ApexSQL Monitor, a Windows and SQL Server monitoring tool able to track SQL Server wait types, including the individual query wait statistics

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