My /var/log/messages is filled with messages like.. Apr 13 05:36:52 pressure smartd[2553]: Device: /dev/sda, SMART Usage Attribute: 194 Temperature_Celsius changed from 137 to 141 Apr 13 05:36:53 pressure smartd[2553]: Device: /dev/sdc, SMART Usage Attribute: 194 Temperature_Celsius changed from 113 to 114 If the drives were over 100C, it would be somewhat alarming. Running smartctl -a on the drives, I see.. 194 Temperature_Celsius 0x0002 141 141 000 Old_age Always - 39 (Lifetime Min/Max 16/47) Note the last column. I think it's very likely that '39' is 39C. Reporting the raw value to the log is going to be much more useful. This seems to be the case on all three drives I've tested on in that machine (A mix of maxtor, hitachi and WD's)
The "big numbers" are the normalized values. Those are reported by the firmware and tracked by smartd and therefore reported to the log. The conversion is also defined by the firmware. If you wish to have also the raw values reported you may add '-r' option in the smartd.conf.