Disk health calculation by Acronis Drive Monitor
Why calculate disk's health status?
The calculated hard drive's health shown as percentage provides you a better visual representation of S.M.A.R.T. related problems.
Health status warns you of disk degradation, when S.M.A.R.T. reports a problem.
This will help you to protect your data before your disk fails.
How to calculate disk's health?
Initially a hard disk has 100% health condition.
All S.M.A.R.T. parameters considered by Acronis Drive Monitor as critical for a hard drive (if they are available for monitoring, it depends on the manufacturer), decrease the calculated health status of your disk. Such attributes have a predefined weight and a maximum limit value (see a Table 1 below).
A limit defines how much the attribute may decrease an overall health value. A weight of an attribute defines how important the parameter's value decreasing the affected the disk's health.
The overall disk health is calculated by the formula below:
Disk health (%) = П (100% - (min(limit, attribute_value*Weight)))
- 100% - initial health of the disk;
- П - the product of minimums from (limit, attribute_value*Weight) - calculated for each critical S.M.A.R.T. parameter;
- Weight - weight of each critical S.M.A.R.T. parameter (see a Table 1 below);
- limit - limit of each critical S.M.A.R.T. parameter (see a Table 1 below);
- attribute_value - current parameter's value.
- Soft Read Error Rate = 30 (attribute value), weight = 1, limit = 20;
- Spin Retry Count = 12 (attribute value), weight = 2, limit = 50.
- So in this case the disk's health is calculated as the following:
Disk health = (100% – (min(30*1, 20))) * (100-min(12*2, 50))) = 80%*76%=60.8%≈61%
The following table contains the health related (critical) S.M.A.R.T. attributes affecting the health value with their weights and maximum limits.
|Attribute ID||S.M.A.R.T. attribute||Weight||Limit %|
|05||Reallocated Sectors Count||2||70|
|10||Spin Retry Count||2||50|
|196||Reallocation Event Count||1||40|
|197||Current Pending Sectors Count||1||40|
|198||Offline uncorrectable Sectors Count||2||70|
|201||Soft Read Error Rate||1||20|
Not critical parameters:
Other S.M.A.R.T. parameters, which have a predefined by manufacturer threshold value, also affect disk's health: after decreasing below the threshold, this parameter subtracts 10% from the current disk health. This means, when the current health is 90%, 9% will be subtracted.
Table 2 shows non-critical S.M.A.R.T. parameters, that affect disk’s health.
|Attribute ID||S.M.A.R.T. attribute|
|01||Raw Read Error Rate|
|03||Spin Up Time|
|07||Seek Error Rate|
|08||Seek Time Performance|
|09||Power-On Time Count|
|12||Drive Power Cycle Count|
|221||G-Sense Error Rate|
|228||Power Off Retract Cycle|
|225||Load/Unload Cycle Count|
|199||Ultra ATA CRC Error Count|
|193||Load/Unload Retry Count|
What else may decrease disk's health?
When a disk is monitored using a custom script:
exit code is 0 : Health = (disk health calculated by S.M.A.R.T.) * 100%
exit code is 1 (warning): Health = (disk health calculated by S.M.A.R.T.) * 50%
exit code is 2+ : Health = 0%
Factors not affecting disk’s health
- Decreasing value of a non-critical parameter does not affect the disk’s health until it is above a threshold, specified by the disk's manufacturer;
- Event log entries also do not change the overall disk health, but still can generate Warnings or Errors.