Add more prominent warning if SMART features are disabled/impaired

[Stilez]

I just bought a Seagate SAS-3 HDD ST8000NM0075. I notice it wasn't producing SMART data although SMART was enabled, and eventually discovered the GLTSD bit, which apparently comes preset to "on", disabling SMART attribute storage (I think - a bit hazy about this!). I've just disabled it and hoping that helps.

The point being, this restriction wasn't obvious in the smartctl output at all. It's true that if I read every line of smartctl -x, there's a mention buried somewhere round line 300 about "GLSTD" being "off", but the term doesn't mean anything to most people who own or use a hard drive, and most won't dig into such output and question every line.

So this is a request, if there is a reason why smartctl thinks it might be impaired in its drive interrogation, due to SMART being disabled, SMART data or log storage being disabled, expected log pages not being found, etc, can that be stated in a clear prominent way, at the top of the output, so it's not easily missed?

It doesn't have to take much room. Just stating "Diagnostic output may be incomplete, due to disabled or inaccessible features on this device: <brief list>." would be enough.

Thanks!

[Christian Franke]

Changing long standing smartctl output may break existing applications which parse the output. Therefore this is only done if really necessary.

For SCSI/SAS devices, smartctl -l error (included in -x) prints the following if GLTSD bit is set (since 2003, see r1260):

[GLTSD (Global Logging Target Save Disable) set. Enable Save with '-S on']

This is IMO sufficient to see that -S on is recommended.

[Christian Franke]

Changing long standing smartctl output may break existing applications which parse the output. The current message is sufficient to see that -S on is recommended.