SMART Fail with Reallocated Sector Count 0

[delcampo95]

My HGST HDD () started flagging a SMART error during BIOS, so I ran DiskCheckup, and I got the following error (and only this error):

Reallocated Sector Count
Status: FAIL
Value 1
Worst 1
Threshold 5
Raw value 0

Does the raw value of 0 mean that no sectors have been reallocated? And if so, why is an error being flagged? And finally, should I backup and replace this hard drive?

[David (PassMark)]

Each different manufacturer uses the SMART values in different ways.
The Reallocated Sector Count raw value should normally count up to indicate the number of sectors that are bad (which means low values are good). But I did some searching on the web, and for at least some Hitachi models, this value never seems to change and the normalised values are more important (which are the "Value" and "Threshold" columns in DiskCheckup).

The normalised values start at 100 and count down, until the threshold is cross, at which point you get a warning.

So yes, I would backup the drive and prepare for failure.