Oddball temp reporting in smartctl

[oshunluvr]

I was looking at my syslog and noticed these messages:

Mar 26 08:59:52 office smartd[1628]: Device: /dev/sde [SAT], SMART Usage Attribute: 194 Temperature_Celsius changed from 107 to 105
Mar 26 08:59:53 office smartd[1628]: Device: /dev/sdf [SAT], SMART Usage Attribute: 194 Temperature_Celsius changed from 101 to 109

OK, I'm a US citizen so I don't know much about Celsius, but I'm pretty sure I could fry eggs at 105° C.

So l couple of quick entries later:

stuart@office:~$ sudo hddtemp /dev/sde
/dev/sde: Hitachi HDS721010KLA330: 57°C
stuart@office:~$ sudo hddtemp /dev/sdf
/dev/sdf: Hitachi HDS721010KLA330: 55°C

That looks much more sane. So smartctl says:

194 Temperature_Celsius 0x0002 105 105 000 Old_age Always - 57 (Min/Max 15/69)
194 Temperature_Celsius 0x0002 109 109 000 Old_age Always - 55 (Min/Max 15/73)

So clearly, what smartd is logging isn't a meaning number. I assumed the numbers 105/109 were °F but the conversion says not. 105°F equals 40°C

Anyone know what 105/109 really mean?

[oshunluvr]

I did some more research. Turns out the 105/109 are "normalized temperature" whatever the heck that is. I did discover a way to make it report the actual raw temp.

In /etc/smartd.conf:

# Alternative setting to report more useful raw temperature in syslog.
DEVICESCAN -R 194 -R 190 -R 231 -I 9

# Alternative setting to report raw temperature changes >= 5 Celsius
# and min/max temperatures.
DEVICESCAN -I 194 -I 190 -I 231 -I 9 -W 5

We'll see how this works...