What is FSAgent.exe and why does it have lots of waits?

Another quickie today. If you're using Activity Monitor in SQL Server 2008, or Performance Data Collection with the Server Activity system data collection set, then you may see a constant, and large number of 'Other' SQL Server Waits. When you drill into these, you see that the highest number of waits are for FSAgent. The FSAgent is part of the FILESTREAM subsystem, and it's what fools the rest of the Storage Engine into accepting the FILESTREAM data as if it was real varbinary(max) data. If you look in the Books Online entry for sys.dm_os_wait_stats, which defines all the different wait types, it explains that the wait should only show up when FILESTREAM I/Os are occuring. However, this wait type shows up *all* the time – clearly a bug.

Turns out that it's a known bug that's been fixed – see KB 958942.

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