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    Copyright © Nancy Hidy Wilson, 2010-2013. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Nancy Hidy Wilson and nancyhidywilson.wordpress.com with appropriate and specific direction to the original content.
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The Case of the Odd CPU

I love mysteries – always have.  I think I had read every volume of Alfred Hitchcock and The Three Investigators and of course Nancy Drew by the time I was finished with fourth grade. I loved trying to figure out the answer to the mystery before it was revealed. Of course, the authors of these mysteries (and even the ones I read today) always held back some key detail that they didn’t reveal until the end that helped to put all the pieces together and solved the puzzle.

A while back, my team was presented with a “mystery”.  Our rock solid automated installation process for SQL Server 2005 was suddenly failing intermittently and we had not made any changes to our installation scripts. But, something had obviously changed in the environment that was causing the failures.

After troubleshooting the SQL Server installation logs for error messages, we found we had encountered a known problem which thankfully already had a documented workaround (http://support.microsoft.com/kb/954835).  The change causing the problem was that we were now getting virtual servers delivered with an odd number of CPUs as seen by the OS and SQL Server. For the additional CPU\core scenarios which can cause an installation failure of SQL Server 2005, please reference the KB article. This issue has actually been documented several years, so it isn’t a new thing, but it was a new condition to us in our environment. If you still find the occasional need to install SQL Server 2005, then you may have a good chance of encountering this condition if you haven’t already.

However, just performing the workaround wasn’t the end of the story for us.  Like any good mystery, there are often “loose ends” to tie up once the main mystery is solved. In our case, we have a post-install configuration script to allocate multiple tempdb files based on a ratio to the number of processors detected. But, our script, which was also applicable to our SQL Server 2008 environment, expected the number of processors to always be a power of 2! As we learned the hard way – that may not always be the case now.

Lessons learned\confirmed:

  • If a process breaks which worked previously, something changed!
  • The impact of the “change” may reach beyond whatever drew it to your attention initially.
  • Expect change and when possible plan for it.

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