(Look in the Misconceptions blog category for the rest of the month's posts and check out the 60-page PDF with all the myths and misconceptions blog posts collected together: CommonSQLServerMyths.pdf (732.96 kb))

Resource governor is a great feature in SQL Server 2008, but there are some misconceptions about what it can do...

Myth #22: resource governor allows governing of IO activity.

FALSE

Resource governor does not govern IO activity in any way - hopefully that will be something that's added in the next major release of SQL Server. It'll be a lot more useful once you can use to prevent run-away queries doing huge table scans, or spills into tempdb.

Some other things that resource governor does *not* do in the first version:

• Allow governing of buffer pool memory. The memory governing it performs is for query execution memory grants only - not for how much space is used in the buffer pool by pages being processed by a query.
• Allow two instances of SQL Server to cooperatively govern CPU and memory resources. Multi-instance governing has to be done with Windows Server Resource Manager, and then with resource governor for each instance.
• Allow a connection to be notified that it has been governed in some way.

Don't get me wrong - it's great, but it will be a lot better with these additions too.

 Our friend and fellow-MVP Aaron Bertrand (twitter|blog) and SQL PM Boris Baryshnikov wrote a comprehensive whitepaper that you should read for more details: Using the Resource Governor.