[smartmontools-support] Can't enable SMART on WD20EARS

[Yuri <yu...@ra...>]

-a flag tells me device is capable but SMART isn't enabled. -s on says 
that it is enabled. And -s again tells me SMART isn't enabled:

$ smartctl -a /dev/ad4
<...skipped...>
SMART support is: Available - device has SMART capability.
SMART support is: Disabled

SMART Disabled. Use option -s with argument 'on' to enable it.

$ smartctl -s on /dev/ad4
smartctl 5.41 2011-06-09 r3365 [FreeBSD 8.2-STABLE amd64] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF ENABLE/DISABLE COMMANDS SECTION ===
SMART Enabled.

$ smartctl -a /dev/ad4
<...skipped...>
SMART support is: Available - device has SMART capability.
SMART support is: Disabled

SMART Disabled. Use option -s with argument 'on' to enable it.
====end commands====


What's likely to be a problem with this drive?

Model Family:     Western Digital Caviar Green (Adv. Format)
Device Model:     WDC WD20EARS-00MVWB0
Firmware Version: 0909
Device is:        In smartctl database [for details use: -P show]

Yuri