Another method of calculating health is to calculate the health based on the percentage of spare blocks in the SSD as a percentage of the total spare blocks in the SSD. The basis of this calculation theory is that when the flash memory is gradually worn out, the spare block is consumed to replace the bad block, and the more the spare block is consumed, the more the health display value is lowered. Some SSD vendors and some hard drive detection software use the remaining spare block method to display the percentage of health.
As the flash wear leveling algorithm becomes more and more robust, the health measured by the remaining spare block method cannot accurately predict the life expectancy of the solid state hard disk: the wear level of all flash memory cells is very close, and it is possible to generate a large number of bad blocks at the end of the burst. As a result, the spare block quickly falls, and the health is suddenly reduced from 100% to the end, which cannot be used as a reminder.