@climagic Another way to approach it is (using typical Linux/UNIX implementation) that each file that you can see in a directory is a directory entry pointing to an inode. Usually there's only one directory entry referencing an inode, so when you delete it, the inode is marked as free, as are indirect blocks and data blocks referenced by the inode. A free block is usually not zeroed. Lots of inode images around.

Kudos for including the overprovisioning (wear leveling) blocks used by hardware.