A few days ago, I began to assemble a backup server. Four Western Digital Caviar Green 2TB drives were bought, and the rest of the parts were scrounged around for. After everything was assembled, problems started popping up.
After poking around in the BIOS, I started installing Ubuntu Server 11.04. Only after most things had been installed (just a few packages before GRUB runs) did the installation fail. I swapped optical drives. No luck. I used a USB drive as the installation media. No luck. I unplugged everything except the basic essentials (including the new drives). Again, no luck. Finally, I ran memtest, and that found tens of thousands of errors around the 200-300MB mark. I pulled one of the memory sticks, and that solved my problem. Frustrating, but if that's the worst of it, this'll be pretty easy.
It installed beautifully, and I proceeded to build a RAID5 array (totaling a 6TB partition), formatted to XFS, just for fun. I set up Samba logins and set permissions. Everything was going smoothly. Small, single-file tests were incredibly zippy (after the RAID array was done syncing). But when anything larger was transferred (bigger than the cache), it would choke the transfer speed down to abysmal speeds (tens to hundreds of KB/s). Since I've never used this particular filesystem before, I started blaming XFS and switched to EXT4. It might have been faster, but not much. After some research, I stumbled across a program called WDIDLE3. To save energy on the Green drive series, the drive parks the heads after a certain period of inactivity. After some poking around, it turned out that it was parking the heads about once per second. Western Digital claims that the drives are rated for 300,000 "head loads". When I noticed it, all of the drives had already accumulated a "load/unload count" (SMART attribute 193) of over 20,000.
I quickly downloaded and burnt an Ultimate Boot CD (which has WDIDLE3 and FreeDOS already on it). Then, I simply booted to it, found WDIDLE3, and ran it. Upon reviewing the options, I chose to "disable" the idle timer. Reboot time.
Doing more tests produced the same results as before. Finally, I booted into FreeDOS and ran WDIDLE3 again, but this time I manually set the timeout to 5 minutes (300 seconds). One, final reboot and set of tests. Success! 40-70MB/s over GigE! After checking SMART, I started a really big transfer and went away for an hour. When I came back and did the SMART tests again, no head loads had occurred!
The moral of the story is not that WDC Green drives are bad, but they need to be tweaked before you start using them. If you don't, you might end up with a dead drive in a matter of months.
P.S.: Just because WD rates their drives for 300,000 head loads doesn't mean they're absolutely going to fail right when you hit the "limit". There are screenshots of people who have 1.3 million head loads, and their hard drive is still working (although they're paranoid about it falling apart at any moment).
P.P.S.: My WD Caviar Black (yeah, the enterprise grade ones) in my desktop report 260 head loads each, and they're several months old.
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