PREEMPTIVE_OS_FILEOPS waits during restore

We received a new server running Windows 2012 and SQL Server 2012 SP1. When we are restoring a database 3.5TB in size split into 24 Data Files and 1 Log file. It takes somewhere between 50-80 minutes where restore does not show sys.dm_exec_requests.percent_complete progress but instead it waits on wait type PREEMPTIVE_OS_FILEOPS whereas our current restores on another Windows 2008 SP2 / SQL 2012 SP1 combination shows a value in sys.dm_exec_requests.percent_complete right away almost. I turned on Trace flags 3004 and 3605 to verify Instant File initialization works on Data files and confirmed only the log file is zero initiated. Our San guys say they do not see any activity during the time the restore waits on PREEMPTIVE_OS_FILEOPS wait type.
What can be causing this long PREEMPTIVE_OS_FILEOPS wait during the restore?

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Gokhan Varol