http://dds6qkxpeiqvogt4y2fd7vtsxq6pvokekb2h4la7jd4iwl4ljuawu5qd.onion/wiki/Dev/Technical_Introduction
The issue with wear leveling is that the disk controller tells the kernel "file deleted," while in reality the sector has been marked as unusable but still contains data. This data can be recovered by data recovery professionals using low-level disk controller commands. This is documented in more detail here: Advice for Solid-state Drives and USB Storage .