WD20EARS dissappears after S3 sleep. It is missing from Windows (not visible in Disk Management), but it is visible in BIOS. The drive will appear again in Windows only after cold restart.
According to Microsoft, the reason for this behavior is that newer large HDDs have longer spin up times after S3 sleep. Windows usually requires the drive to be ready in 10s. If it’s not ready, it disappears from the system and is not visible by Windows.
Microsoft fixed this problem by issuing hotfix KB977178 for Windows 7:
It updates Microsoft SATA drivers to wait longer for HDDs to spin up.
Is there the same update for Vista? The hotfix above works only for Windows 7.
Here is my particular set up that gets WD20EARS disappearing after S3 sleep:
OS: Vista Ultimate x64
SATA controller: on-board nVidia GeForce 9400
I also have lower capacity WD10EADS on the same system - they work just fine with S3 sleep. Both WD10EADS and WD20EARS have virtually the same spin up times reported by SMART - around 6.3 - 6.5 seconds. This is less than 10 s as required by Windows, but WD10EADS works just fine and WD20EARS disappears.
I have checked all SATA cables and installed all latest drivers, Windows and BIOS updates. Power Management settings for the drive are set to never sleep.