S.M.A.R.T. - 78.4%

[bejhan]

What is the significance of 78.4% in the S.M.A.R.T. details? Even the documentation has this exact value.

I'd expect 100% if an attribute is "perfect" (on a new drive, for example) but all of my drives seem to be showing 78.4% at most.

Thanks in advance.

[bejhan]

After a bit of research, I've discovered that even though the maximum value of an attribute is 255, manufacturers choose a maximum value that suits them (usually a nice round number). In WD's case, they have chosen 200 (200 / 255 = 78.4%). I have an HGST drive that seems to be using 100 instead which results in 39.2%.

[Christopher (Drashna)]

You mean the Load Cycle Count, specifically? 

[bejhan]

Actually, many attributes show this value.

[Rob Manderson]

On 2/26/2021 at 9:50 AM, bejhan said:

After a bit of research, I've discovered that even though the maximum value of an attribute is 255, manufacturers choose a maximum value that suits them (usually a nice round number). In WD's case, they have chosen 200 (200 / 255 = 78.4%). I have an HGST drive that seems to be using 100 instead which results in 39.2%.

And that explains something that's puzzled me for years - why I have short bars, even on new drives, when 'longer bars are better.  Most of my drives are seagate and hgst - and an awful lot of them show 39.2% or 78.4%.

[Christopher (Drashna)]

Yeah, it's ... manufacturer fun.   SMART really isn't a standard, it's more of a guideline, that a lot of manufacturers take a LOT of liberty with.  NVMe health is a *lot* better, in this regards (it an actual standard).