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WD10EARS makes "clicking" noise when idle
Quote from NGOHQ.com
It has come to our attention that Western Digital's Caviar Green HDDs suffer from a critical design flaw caused by an aggressive power-saving feature. Western Digital has developed a new technology called Intellipark (aka Idle 3 mode) and it is designed to reduce power consumption, in part by positioning the HDD's heads in a park position and turning off unnecessary electronics after 8 seconds of inactivity.
According to an in-house investigation and user reports', some software and operating systems are incompatible with the Intellipark feature causing endless head parking movement as the HDD continuously goes in/out of idle mode. This abnormal behavior creates stress on the HDD and that could lead to the following issues:
• Loud clunking/clicking/buzzing noises every few seconds.
• Artificially increases the number of load-unload cycles in S.M.A.R.T.
• Possibly shortens life-time of the HDD.
• Possibly reduces performance of the HDD.
And, they mention a fix in the rest of the article, here --> Critical Design Flaw Found in WD Caviar Green HDDs