Please remember that Auto Offline data collection is part of the SFF-8020i
specification, and is NOT part of the ATA specifications. So vendors like
WD are not necessarily going to comply 100% with this SFF-8020i specs,
though I think they try.
In this case there are two different bytes. One (offline data collection
status) is indicating that Auto offline IS enabled:
> Offline data collection status: (0x85) Offline data collection activity
> ------>Auto Offline Data Collection:
The other byte, offline data collection capabilities, that shows the
capabilities of the device:
> Offline data collection
> capabilities: (0x79) SMART execute Offline immediate.
> ------>No Auto Offline data collection
indicates that it's not supported. I suspect that the problem is simply
that the WD firmware people have neglected to turn on the appropriate bit
in the offline data collection capabilities byte.
If '-o on' and '-o off' change the values of the Offline data collection
status byte, then you can be fairly sure that it IS supported. On my WD
Device Model: WDC WD2500JB-00EVA0
it IS supported.