IIS 7.5 2008R2 Standard Edition x64
This same problem happened with me on IIS6 too, but I thought an upgrade would solve it ... I was wrong!
Running with the defaults, everything will be going great, just 4 or 5 PHP-CGI processes spawned, when suddenly, WHAM, another 20 or 30 will load up and all the websites become unresponsive. The PHP-CGI sessions themselves use no CPU, just loads of 0% activity.
After a while (around 6 minutes, this could be the time in my request timeout actually) - suddenly they will all spring into life! With the redundant ones closing down.
Whilst this is going on, an IIS Reset seems to be the only way to get it going again.
Nothing crashes and there is nothing in either the event log, nor the PHP error log file.
Obviously this is not good ;) So any suggestions on how I can troubleshoot this?
thanks!