EMBRON Hatteland HD 19T22, User Manual

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SSD Selection Guide
Appendix
IND100077-130
Calculation / estimation of operational lifetime
Assumed System with Hatteland Technology provided SSD or selected according to guide above.
1. Measure/estimate/calculate average disk usage per day.
For measuring, use SMART data.
o Measure the difference in numbers of write cycles at the start and at end of the test
(or the difference in remaining lifetime)
o Run the test with relevant disk load and during relevant time period
Relevant disk load - should correspond to the average disk load during the operational lifetime.
Relevant time - time it takes to generate relevant disk load with statically significance.
Many SSD manufacturers provide tool for calculating expected operational lifetime.
2. Selection of SSD
Select SSD type/series.
Define minimum expected lifetime [Year]
Define minimum required SSD capacity [GB]
From datasheet,
- check if the endurance is expressed as PBW/TBW or DWPD.
- check warranty [year]
PBW - PetaByte Written = 1000 terabyte written = 1000 000 gigabyte written.
TBW - Total Byte Written normally expressed in terabyte.
DWPD - Disk Write Per Day.
Note relation TBW and DWPD : TBW = DPWD * warranty * 365 * SSD capacity.
Calculate minimum TBW/DPWD.
If TBW in datasheet : TBW = Lifetime *365 * average disk load per day.
If DPWD in datasheet : DPWD = TBW / (warranty * 365 * SSD capacity).
Use datasheet,
Select disk where actual capacity is greater or equal to minimum required capacity
and TBW/DPWP in datasheet is greater or equal to calculated minimum TBW/DPWD.
If lifetime is not according to requirements:
Select different SSD, size and/or type, or use mechanism such as over provisioning to extend the
operational lifetime.