Comment 3 for bug 1653560

Normalization seems to be:

Temperature_Celcius_normalized = 150 - Temperature_Celcius_RAW_VALUE

In my case:

112 = 150 - 38

That said, my hard disk's temperature has 112% health.

Values below 100% mean that the hard disk is hotter than 50°C.

As powersj pointed out, this is documented behaviour. It's not a bug, respectively. Eventually, normalization is done by hard disk vendors, meaning that WD is perfectly fine with 50°C (=100% "health").

It's just confusing, especially in syslog. Eventually, an interpretation could be given in syslog?

E.g.

Jan 2 20:22:27 server smartd[876]: Device: /dev/sda [SAT], SMART Usage Attribute: 194 Temperature_Celsius: Thermal health changed from 110% (40°C) to 112% (38°C)

Additionally, only logging values below 100% health (or a user specified threshold) makes sense to me. If everything is fine, it should not be reported in syslog periodically (by default at least).