I noticed that the new Western Digital WD15EADS disk spun down way too fast. After some serious testing I found: when I set the "Advanced Power Management" level (using hdparm -B) to 127 or less the "standby (spindown) timeout" (set using hdparm -S) is ignored and the drive spins down after
about 58 seconds of inactivity. Way too soon when playing a movie, with mplayer the movie stalls about every 10 seconds because a new bit of movie has to be read from disk which causes another start/stop. The smartctl start/stop counter goes up at the same rate. Feels like a firmware bug to me or a difference of opinion between hdparm and the disk. But the hdparm report suggests that these settings should work on the disk:ATA device, with non-removable media Model Number: WDC WD15EADS-00S2B0 Firmware Revision: 04.05G04 Standby timer values: spec'd by Standard, with device specific minimum Advanced power management level: 126 * Power Management feature setI asked Western Digital customer help about this but the first (standard?) answer is from Support for WD products in LINUX or UNIX which comes down to "we don't support anything else than jumper settings for these operating systems".
A lot of further searching with google suggests to me that the 'IntelliPark' feature is causing the drive to park its heads after 8 seconds of inactivity which is not a useful default when streaming video from it with a reasonable cache. And the 'Load Cycle Count' will go up fast, which may result in the drive reaching the 'suggested maximum' within a year. I don't need to test the warranty that fast.As a workaround I set the Advanced Power Management level back to 128 and installed spindown which is a utility which watches the disk activity from userspace and issues a spindown command when no activity (from /proc/diskstats, so for linux at the device level) was measured over the configured period of time. Now it spins down when the filesystems have been idle for 10 minutes which is a lot more usable.
Update: Official answer from Western Digital customer help is that it's not possible to change this 8 second timeout. So I'll stick to the spindown solution. Update 2: Robert Waldner also noted this problem and described how to change the idle timeout / "IntelliPark" time on Western Digital Caviar Green disks.