[smartmontools-support]Re: that wd 190 smart attribute i was complaining about

[Bruce A. <ba...@gr...>]

Jason,

> i spoke with wd again and it is apparently some half implemented pcb 
> airflow sensor.

I have been experimenting with 640 (no, not a typo) Western Digital disks 
on our new cluster (Nemo).  They are:

  Model Family:     Western Digital Caviar SE (Serial ATA) family
  Device Model:     WDC WD800JD-08LSA0

I have determined that on these disks, Attribute 190 is a monitor of the 
MAXIMUM temperature ever detected by the disk.  The raw value is the max 
temp in Celsuis.  The failure threshold is set so that if the disk reaches 
55 Celsuis (max operating temp) then the normalized value drops to the 
threshold threshold and the disk is marked as a 'usage failure'.  Here is 
an example:

ID# ATTRIBUTE_NAME     VALUE WORST THRESH  TYPE      UPDA    WHEN_FAILED RAW
190 Unknown_Attribute   064   044   045    Old_age   Always   In_the_past 36
194 Temperature_Celsius 107   088   000    Old_age   Always       -       36

In what follows I refer to Attribute 190.

The raw value indicates that the CURRENT disk temperature is 36 Celsuis. 
The normalized 'VALUE' decreases by 1 for each 1 Celsius increase in 
temperature.  The sum of 'VALUE' + 'RAW' is always 100.  Thus the 'WORST' 
value of 44 indicates that at some time in the past the disk temperature 
was 56 Celsius.

In smartmontools 5.37 I have changed the name 'Unknown_Attribute' to 
'Temperature_Celsius'.  The only difference with Attribute 194 is that 
Attribute 194 has its failure threshold set to zero so it can never fail.

Cheers,
 	Bruce