July 8, 2014 at 12:48 pm
Experts:
We are running SQL 2008R2. Our production data spans across three datafiles D:\, E:\ and F:\ connected to storage.
Overnight, one of the driver letters disappeared. The issue wasn't reported till several hours later. We rebooted the OS, and the drive letter returned. We are addressing this issue with Microsoft and VMWare.
Question: What really is the impact here to the data with one the data files that went missing for several hours ? I'm told that some of the reports that access / write to the production tables appear to be fine. I'm running DBCC checkDB across all production databases but wanted to get a better understanding of what happened. How can a database continue to work with one of its data files missing ?
Thank you
Jay
July 8, 2014 at 1:52 pm
Basically, buffer pool. SQL caches data in memory and works off that. It won't go to disk unless what it needs is not in the buffer pool.
You got lucky. If SQL had needed to read from that file if would have declared an IO failure and you'd probably have needed to restore from backup.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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