I use a 1 TB KIOXIA-EXCERIA G2 as the boot drive in my daily-use PC. It is rated for 400 TBW, has about 14,000 hours of power-on time, and reports 112 TB written by the operating system. However, CrystalDiskInfo shows the drive health at 48%, down from roughly 51% two months ago. I have usually kept the drive fairly full, although I recently started leaving 200–300 GB free. There are currently no reported media or data integrity errors. What could be causing the health percentage to fall faster than expected, and should I replace the SSD immediately?
2 Answers
TBW is a warranty endurance estimate, not a precise countdown timer. The reported health can also reflect the drive's actual wear, retired NAND blocks, error history, overprovisioning, or even how the firmware interprets its SMART data. It is possible, though less certain, that the firmware is using an incorrect endurance figure for this model. A declining percentage deserves monitoring, but the lack of media errors and a healthy available-spare value are more reassuring than the percentage alone. Make sure important data is backed up and replace the drive when SMART warnings appear, spare capacity drops toward its threshold, errors begin increasing, or you simply need greater peace of mind—not solely because the health display says 48%.
The health percentage and the host-written total are probably measuring different things. A drive rated for 400 TBW may be estimating wear based on data written internally to the NAND, not just the 112 TB reported by the operating system. SLC-cache management, garbage collection, and rewriting data can make the NAND write considerably more than the host-write figure—especially when the drive has spent much of its life nearly full. A drop from 51% to 48% can represent normal background NAND traffic rather than an imminent failure. Since there are no media or integrity errors, this does not by itself suggest that the SSD is about to die. Keep backups, leave some free space, and monitor the SMART attributes, particularly the available-spare value.
The available-spare value is still 100, while its warning threshold is 5, so that attribute currently looks healthy.