Found some info...
So after one of my WD20EADS 2tb Green drives failed I came across some research on other forums that pointed out that one of the features of the Western Digital green drives is "Intellipark".
What is Intellipark you ask? Well its a "feature" on these green drives that parks the head every x seconds of inactivity, the default being 8 seconds for both read & write. This feature is fine for Windows, but as I am running my disks in RAID 1 on a Linux machine with many reads & not many writes, I encountered some problems.
Because these disks are being used in Linux, it basically causes unending park/unparks of the head, due to the way Linux's I/O works. It is my understanding that Linux reads data into a buffer every 20 seconds, so therefore the data was being read, then 8 seconds later the head was being parked, then another 12 seconds later more data was read.
Can you see the problem?
Another issue consumers are experiencing is the disk being kicked out of a RAID array due to Time Limited Error Recovery being disabled. TLER is a feature available on Western Digital's premium, higher-priced range of RAID enabled drives, and luckily, we can enable it on our green drives
Fortunately there are ways around these issues.
DISCLAIMER: Perform these tweaks at your own peril! I've heard reports that this may void your warranty. Hell you will probably lose data too so don't forget to back up!
To enable these fixes, you will need to unplug any drives you do not wish to apply these fixes to, and then you will need to boot into DOS using your favourite boot disk.To fix the head parking issue:
A utility once released by Western Digital called WDIDLE3.EXE
is available from http://www.synology.com/support/faq_show.php?lang=enu&q_id=407
What this utility does is allows you to change the time until the head is parked on your drive(s), or disable it completely.
WDIDLE3 [/S] [/D] [/R] [/?]
/S Set timer, units in seconds. Default=8.0 (8.0 seconds).
Resolution is 0.1 seconds from 0.1 to 12.7 seconds.
Resolution is 30 seconds from 30 seconds to 300000 seconds.
Note, times between 12.8 and 30 seconds will be set to 30 seconds.
/D Disable timer.
/R Report current timer.
/? This help info.
Simply running "wdidle3 /D" should be enough to disable Intellipark, but if you run into issues, I've read that "wdidle3 /S0" works instead. Either that or you can set it to some ridiculously huge amount.
To enable TLER:
You will need the WDTLER utility available here: http://shifteightgeneration.com/content/wdtler-fix-tler-setting-wd-desktop-hard-drives
First of all, make sure your drives are in "IDE Mode" in your BIOS settings.
You can simply run "TLER-ON" to enable TLER with a default of 7 seconds, and "TLER-OFF" to turn it off. Both of these are batch files included with the utility. If you are running off a hardware RAID card, I recommend you check with your manufacturer as to what to set your TLER setting to.
I can confirm that both of these utilities work on my replacement WD20EADS-00R6B0 which I received today & was eager to apply these fixes to. I'm awaiting my other drive to fail so that it can be replaced under warranty before I bother with it, the head has probably been parked more than I want to think about!
I really hope this helps someone as I had to search about 20 different threads on Google to get the info I was looking for.Edited by WeAreNotAlone - 12/31/10 at 11:40pm