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All,

I'm in the process of evaluating SQL AlwaysOn, and everything is failing over as expected, except in one circumstance, when the disk goes belly up. In this case, SQL does nothing, other than present the following two errors.

Dash board error as well as when i go to the properties of the DB

The error makes sense, as I've dropped the drive that also contains TempDB, but what concerns me, is dropping the drive doesn't seem to be catastrophic enough to cause a fail over.

Am I missing something here? I tried adding the drive to wsfc, but because its not a clustered drive, it doesn't seem that it will work, as each individuals servers drive shows up as a separate resource.

Edit 1: The only event log entry is as follows. Once again, pretty much an expected error.

The operating system returned error 21(The device is not ready.) to SQL Server during a read at offset 0x00000000382000 in file 'E:\Data\vcdb.mdf'. Additional messages in the SQL Server error log and system event log may provide more detail. This is a severe system-level error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.

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  • I guess as you can see, SQL also doesn't seem to see a fault in the DB either.
    – Eric C. Singer
    Apr 15, 2013 at 20:00
  • So... did you check the event log? Did it have anything in there?
    – Mark Henderson
    Apr 15, 2013 at 20:36
  • Hi Mark, see my edit. Nothing that i wouldn't expect.
    – Eric C. Singer
    Apr 16, 2013 at 12:48

1 Answer 1

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Losing a database file, even one as critical as the tempdb file, is still a database-level event.

According to this Microsoft Technet article:

(Failover and Failover Modes (AlwaysOn Availability Groups) )

Issues at the database level, such as a database becoming suspect due to the loss of a data file, deletion of a database, or corruption of a transaction log, do not cause an availability group to failover.

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  • Thanks, although i would still like to see a "disk" failure cause a fail over. Meaning a HW event not a DB event. The DB going offline would merely an effect of the HW going offline.
    – Eric C. Singer
    Nov 17, 2013 at 17:55
  • I completely agree. Common sense expectations would see a failover with disk failure. But I think the documentation here is distinguishing between the SQL Server Service availability and the underlying OS/hardware availability. It does have a "Lawyer Ball" flavor to it, but I think this is intended functionality (or at least, MS considers it "as designed")
    – peterk411
    Nov 18, 2013 at 22:18

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