We had a case over the weekend where our automated restore process at client got hung up on this wait type, for a single database. What was the unique characteristic about this relatively medium (2-300 GB) database? It had a lot of filestream data–it seemed like the file count wasn’t that high, but my guess is the filestream data was the majority of the data in that database. When the job hung up, the restore had been waiting on PREEMPTIVE_OS_FILEOPS for over a day and still had a null value for percentage complete.
Click through to see what the problem was.