preface: yes i've searched the archives/google but couldn't find an explanation for what i'm seeing.
i've got a problem with smartctl failing to show the S.M.A.R.T. attributes on one of my clients Macs which has a WDC WD7500BPKT-75PK4T0.
the problem is that smartcl would "sometimes" succeed showing the attributes or starting a short test and sometimes just give this instead:
> smartctl 5.43 (build date Apr 27 2012) […snip…]
> Smartctl: Device Read Identity Failed: Unknown error
> A mandatory SMART command failed: exiting. To continue, add one or more '-T
> permissive' options.
this is both with revision 3314 from some time back as well as with a newer build from late april 2012. of course i've already added "--tolerance=permissive". i've also looked at the source for what the cause of the "unknown error" could be, this didn't help either.
what is puzzling me is that the problem occurs just sometimes, while it succeeds at other times, and i can't see any clear reason or pattern for it only working randomly.
does anyone have any ideas? could it be connected to the device not being "in the database"?