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Beyond deleting the reference to file , Delete the data on disk means one of two things : Overwrite with zeros or have another file contents written over it .

Beyond deleting the reference to file , Delete the data on disk means one of two things : Overwrite with zeros or have another file contents written over it . Overwrite with zeros is generally not done as default in flash memories to improve disk life, flash memories have a limited number of times they can be written too, so most memory controllers will try to distribute writes This seems less a OS bug, more likely iOS/iCloud had a bug on marking deletion correctly

jasomill 2y ago
"Overwrite" on flash requires erasing the block containing the data you wish to overwrite, so pre-erasing blocks that will never be used again until rewritten doesn't reduce available write cycles, and can improve both endurance and performance. Two potential issues when relying on flash erasure for privacy, neither of which apply to a full device wipe: 1. Filesystem allocation units are almost always smaller than flash erase blocks; erasing and rewriting, e.g., a 1MB flash block whenever a single 4 kB allocation unit it contains is freed will lead to performance and endurance problems. 2. On desktop and laptop systems, erase (ATA TRIM/SCSI UNMAP/NVMe Deallocate) operations are typically deferred to a low-priority or periodic background task for performance reasons; the same may apply to iOS devices. In the case of full device wipes on modern Apple devices (iOS and Apple Silicon Mac), this is mostly moot anyway from a privacy perspective, because encrypted storage makes data effectively unreadable as soon as encryption keys are wiped.