Re: [Smartmontools-support]A series of questions

[Christopher W. <sma...@th...>]

At 06:49 AM 2/22/2003, Bruce Allen wrote [edited response]:
> > Can someone explain what several columns are?  What are the flags and what
> > do they mean?
>
>The flags are "proprietary" or "vendor-specific", meaning that they don't
>have a fixed meaning given by the ATA/SMART specs.  However from
>historical useage, the least significant bit of the flag indicates
>Pre-fail (versus Usage) attributes, as indicated in the TYPE column. IBM
>does document a couple of the other bits, but as far as I know they are
>the only manufacturer to do so.
>
> > What is the difference between VALUE and RAW_VALUE?
>
>Again, please read the smartctl man page.


I had looked for this information in the man page before and not found it, 
so I re-read the whole thing in detail and finally found a brief mention 
under the discussion of the -A option, where I had not expected to find 
it.  Might I suggest breaking this out into it's own section?

What I did find says:

    Each Attribute has a 'Raw' value, printed under the
    heading  'RAW_VALUE',  and  a  'Normalized'   value
    printed under the heading 'VALUE'.  ...
    Each  vendor  uses  their own magic to convert this
    Raw value to a Normalized value in the range from 1
    to 254.

    Note  that  the  conversion  from  'Raw' value to a
    quantity with physical units is  not  specified  by
    the  S.M.A.R.T. standard.

Expounding on this, the raw value is the value actually reported by the 
disk, which smartmon then interprets via some unspecified logic to come up 
with a "Normalized" (how?) result that it displays as the actual VALUE, and 
it has to guess at this because each manufacturer uses a different method 
to do the conversion since its not part of the SMART spec?  Or does the 
manufacturer do the conversion and smartmon just reports it by reading it 
from the drive? What about the THRESH and WORST values?  Does smartmon 
produce them or read them from the disk?


> > What does it mean when the threshold is zero?
>
>This means that the attribute can never fail, since the attribute fails if
>its value is less than or equal to the threshold, and the minimum
>attribute value is 1.


So those attributes are only for "tracking purposes" or informational 
purposes?  What about something like

   3 Spin_Up_Time            0x0003   072   070   000    Pre-fail     -       0

I assume that VALUE/WORST are the only attribute values that have a minimum 
of 1, since the THRESH is obviously zero here, as is the raw value.  So how 
do I interpret this pre-fail attribute with a 0 threshold?



> > 194 
> Temperature_Celsius     0x0022   083   079   042    Old_age      -       44
> >
> >
> > Is this telling me the temperature is 83 degrees Celsius?  I doubt that ...
>
>It probably IS the temperature attribute.  Again, as explained in the
>smartctl man page, 44 Celsius is the drive temperature (internally, as
>reported by the drive.)  The normalised value of this quantity is 83.
>This value has (at some point in the past) had value 79, which means that
>the drive has in the past been hotter than it is now.  In order to "fail"
>the usage threshold the normalized value has to drop to 42 or lower.


OK, thank you for the explanation.

As I understand it then, the normalized values are then merely an 
algorithmic representation of the raw data, and the raw data may itself may 
have several meanings depending on manufacturer.  These algorithmic values 
have no real world representation (like the raw value might, but doesn't 
always), and are merely an abstract measure of how close that tracked drive 
attribute is to an "incorrectly operating" failure level.  The 
value/worst/thresh can only be compared to each other, and only for a given 
attribute, and the values are derived through a "magical manufacturer 
conversion" of the raw value.  This, then, answers my question above in 
that smartmon does not calculate these values, but merely reads them from 
the drive.

I don't really see that explanation in the man page, and it could probably 
use additional discussions on that topic to clarify.



> > Next, on several of the drives, I get this in the headers:
> >
> > Seagate ST340016A: ATA Standard is:  Unrecognized. Minor revision code: 
> 0x00
> > WDC WD1000BB-75CHE0: ATA Standard is:  Unrecognized. Minor revision 
> code: 0x00
> >
> > What does this mean?
>
>It means that Seagate/WDC is not completely obeying the ATA spec.  The ATA
>spec for ATA-5 (which is what the Seagate drive is) actually consists of a
>dozen different revision levels.  The manufacturer can put a non-zero
>number in the minor revision code, which indicates (indirectly) which of
>these different revisions is the one that the drive obeys.  But Seagate
>hasn't bothered to do this.


So this isn't an error/problem in the drive, but merely an unsupported 
feature.  Maybe there's a better way to display that so it gets across that 
this is just not being used by the drive, as compared to being a possible 
error?



> > Since the Seagate tools can run and log the tests, I'm wondering why I
> > can't from Linux.
>
>That's interesting.  Could you please post the complete output of the
>self-test log as reported by the Seagate DOS tool, and tell us about your
>kernel version and build?


I'll do so in a separate message, as there's a lot of data there.


>Second, smartd automatically enables SMART (equivalent of -s on) on the
>device, "just in case" SMART has been disabled.


Perfect!  Thanks.

-W