Head parking is excellent... the issue I think he is referring to is that green drives supposedly park after 8 seconds of inactivity and AFAIK also shut down their motor... this has been referred to as head parking issue by most (although personally I think the motor shutting down is a bigger concern), it happens regardless of what you set your OS's power saving to (in all other drives you can set it in the OS, and it typically defaults to 20 minutes of inactivity)
the "keep failing in WHS" is an issue concerns me... that rapid sleep feature of caviar green drives should not cause them to appear as failed drives. but according to google results I found it appears that WHS is an even bigger piece of fecal matter than I though. Apparently it does.
WHS will consider the drives to have failed over this slight delay in spinup... because WHS is a POS and nobody should be using it. seriously, you shouldn't. It has dataloss issues. Go and get FreeNAS from
http://freenas.org/ and use it in ZFS mode
I personally use green drives in an opensolaris ZFS raidz2 (raid6 equivalent)... every time i access data there is a few second delay since the motor is always off and heads always parked. I have no issue with it though. ZFS will never decide your drive failed due to spinup delay, or data recovery delay (TLER)... because ZFS is not a POS
you can supposedly alter the behavior of the drives with a tool called WDIDLE3.exe
google for it if you must; but I seriously suggest you move from WHS to a proper OS.