I have a 240GB Intel 520 SSD and have been puzzled by the behaviour of the SMART statistic 'Power-on Hours Count' (Attribute 09) displayed by the Intel SSD Toolbox utility. Others have also noted that this Power-on Hours Count statistic is strange and so this is not a fault that is specific to my SSD.
Intel have acknowleged that there is an issue with the SMART statistic 'Power-on Hours Count' -
It would seem useful to know:
- Do Intel plan to fix this Power-on Hours Count problem?
- Do the Power-on Hours Count values shown have any useful meaning for a given Intel 520 SSD?
- If so, then does this meaning also apply to other Intel 520 SSD units?
A response from Intel would be appreciated with regard to Question 1.
To address Question 2 I have done some investigation into the Power-on Hours Count behaviour for my 240GB Intel 520 SSD.
My PC was built with the Intel 520 SSD and two rotating disks. I have owned it for over a year and the Power-on Hours times for all three disks should be almost identical (the Power-on Hours Count values for the two rotating disks agree to within an hour).
Looking at snapshots of the Power-on Hours Count values taken at various times over the year it became evident that:
- The Power-on Hours Count values for the two rotating disks were increasing at the same rate.
- The Power-on Hours Count value for the Intel 520 SSD was also increasing, but at a somewhat slower rate.
Over a long period (around a year) the increase in the Power-on Hours Count for my Intel 520 SSD was 0.926 times the increase in the Power-on Hours Count values for the rotating disks. This seemed rather strange!
If the two rotating disks were correctly incrementing their counts every 60 mins then the Intel 520 SSD was incrementing every 64 min 48 sec - not a very obvious time period for an hour!
The other issue is that there appears to be a large base offset applied to the Intel 520 SSD Power-on Hours Count. Using the 0.926 ratio and extrapolating backwards it would appear that the base value when my SSD was first powered on was probably approximately 894,813.
So for my 240GB Intel 520 SSD the formula for converting the 'Power-on Hours Count' displayed by Intel SSD Toolbox (PoHC) into the actual Power-on Hours seems to be:
Actual Power-on Hours = (PoHC - 894,813) / 0.926
Does this formula (or a similar one) also work for Intel 520 SSDs owned by other users?
(See Question 3 above).
Some follow-on questions arose:
- Do my rotating disks actually increment the Power-on Hours Count every 60 mins?
- Does my Intel 520 SSD actually increment the Power-on Hours Count every 64 mins 48 sec?
This was rather difficult/tedious to investigate using Intel SSD Toolbox so I used a utility called System Information Viewer (SIV) from rh-software.com, which made the investigation much easier (I used Menu -> Tools -> Disk Status and left it running for a number of hours).
This showed that:
- My rotating disks do increment the Power-on Hours Count every 60 mins.
- The interval at which my Intel 520 SSD increments the Power-on Hours Count varies by several minutes. The shortest I have seen so far is 62 min 49 sec and the longest is 67 min 4 sec. (The mid-point between these values would be 64 min 57 sec, which is reasonably close to the long-term average of 64 min 48 sec mentioned above)
Do Intel 520 SSDs owned by other users also show this significant variation in the time taken to increment the Power-on Hours Count?
So in summary I have learnt that:
- The interval at which my 240GB Intel 520 SSD increments the Power-on Hours Count varies by several minutes, with a long term average of about 64 min 48 sec.
- My 240GB Intel 520 SSD Power-on Hours Count has a large base offset of approximately 894,813.
Do other Intel 520 SSD users see similar behaviour?