Insufficient HDD-oriented Inspections for SSD/NVMe

SSD/NVMe drives exhibit peculiar phenomena just before failure. They have sectors whose state is uncertain, as they might read, fail to read, write, or fail to write. This is because HDDs read and write through mechanical action, whereas SSD/NVMe drives do so through electronic action plus algorithms.

Equating Full Scan Results with Statistical Scans. It’s no wonder that the results are unstable when mapping full scan results to statistical scans. The factors making data recovery difficult in SSD/NVMe and USB flash drives were found to be here.

This phenomenon was confirmed in NVMe. The full scan is stopped at 96%, and the statistical scan resumes at the resume point. The top shows the “full scan results,” the middle shows the “results mapped to statistical scans,” and the bottom shows the “statistical scan results.” The analytical accuracy under the statistical scan drops significantly. Despite having tested every sector, the actual test was only done in a “spotty” manner. Even with an all-green result, there’s a possibility of “Windows boot failure” just a few days later. Also, this problem applies to Windows’ standard “full format.”

This format performs a full sector check after a quick format. However, if the read doesn’t reach the flash, skipping the check due to “spottiness” doesn’t guarantee safety.

↑ Full Scan (Inspection calling every sector, existing since v1 era)
↑ 完全スキャン (v1時代からある全セクタを呼び出す検査です)

↑ Reflecting Full Scan Results in Statistical Scans (Full Scan Results → Reflected in Statistical Scan [Equated])
完全スキャンの結果を統計スキャンへ反映 (完全スキャンの結果→統計スキャンに反映[同一視])
The range from 0% to 96% is equated from the full scan. The accuracy in the latter half improves, but the accuracy in the first half (shown below) is very low. Of course, there are SSDs where full scans yield accurate results. However, there is no way to know in advance whether the full side will be accurate, so statistical scans are necessary from the start.
0%から96%の範囲は、完全スキャンから同一視されたものです。 後半にかけては良くなっておりますが前半部分の精度(下の図)が非常に低くなっているのがわかります。 もちろんSSDによっては完全スキャンでも精度が出ている場合はあります。しかし完全側で精度が出るのかどうか事前に調べる術がないためはじめから統計スキャンが必要となります。
If the results of the statistical and full scans completely match (in phase), it’s known afterward that the full side had no problems. As an exception, HDDs always yield a constant result (either a normal or bad sector), so only the extremes of the results are taken. In this case, the statistical scan will always yield a constant value (constant), so the results of the full scan are guaranteed to match in advance. Therefore, HDDs can obtain sufficient results with a full scan.

↑ Statistical Scan (Equipped from v3, conducted over the entire range)
The test accuracy below has increased. This analytical result provides reassurance.
↑ 統計スキャン (v3より搭載・全区間を実施)