Quick blog for this one, took me a little while to track down exact problem and fix, so hopefully this will speed someones fix time.
I recently installed a new 2008 R2 cluster on Windows 2008. A week or so after the install, and before it went live, I noticed that the Application log was being spammed every 15 seconds with the error messages
- [sqagtres] CheckServiceAlive: returning TRUE (success)
- [sqagtres] LooksAlive request.
This is a known bug in SQL 2008 R2 and SQL 2012 that has been addressed by Microsoft in the (current) latest CUs. The link for detailed problem can be found here.