Taking life philosophically.
31 January 2010
There is a strange feature on my new Western Digital Caviar Green (WD5000AADS, 500 GB) hard drive. After a period of 8 seconds of inactivity, the drive heads “park” themselves, or go into standby position. This behavior is fine on certain systems, but on my system, it seems inappropriate. This is because almost as soon as the heads are parked, they are activated again. This leads to wild oscillation between the two states. I spent a couple of hours on the net browsing through the forums for other people’s experiences, and it seems many people are concerned about this.
An important term to understand is “load cycle count”. In practical terms it means more or less how many times the heads have been activated. In my case in normal use, after three days (20 hours), the load cycle count had arrived at over 1300. If this is representative of normal behavior, in one hour therefore there are 65 load cycles. According to Western Digital, the drive is specified to endure 300000 load cycles. If the load cycles continued at the rate of the first three days, the drive is therefore specified to continue working for a total of approximately 4615 hours. If we estimate that on an average day a person works for 6 hours on the computer, the count would exceed 300000 in 769 days or slightly more than two years.
Two or even three years seems like a short time. Of course the specifications do not say that the drive will fail right after arriving at that specific number. It is just a specification. However, I do find it worrying.
Generally it is believed that the more the heads are parked, the likelier the drive is to fail. It is possible that WD has found a way around this, and that these drives will continue to work normally even with a high load cycle count.
What can safely be said is that the behavior seems strange. The heads can be parked for many different reasons: to prevent damage to the platters in case the drive gets shaken, or to save energy. As this is a desktop drive and desktop computers are normally on a stable surface, the first issue seems a non-issue. To save energy is a valid goal, but to do this the heads would need not just to park themselves but also to stay in a resting position for a not insignificant period of time. However, on my system the heads seem not to rest at all but spring right back to work. It seems clear no energy is saved.
Some people say that the problem is that the feature works properly in Windows and Mac OS, and some say that the problem manifests itself with all operating systems. It does not matter how that may be. What is important is how to deal with the issue if it appears.
I finally found that Western Digital has made available a tool to adjust and disable the feature that causes the heads to park themselves. It is called “wdidle3”, and since apparently WD does not offer it directly, you have to search for it with Google. I do not guarantee it will work for you and in fact I do not recommend you use it if you do not know exactly what you are doing, but it seemed to work for me. Unfortunately “wdidle3” is a DOS program, which for an Ubuntu user like me meant that I had to set up a FreeDOS boot disk to run it. That done, I disabled the feature with the following simple command:
After this everything seems to be normal. The other “green” features, such as the dynamic speed adjustment, seem to work.