How file recover works

One of my subscribers sent me a private message asking a question which may interest at least some of you, my dear subscribers

He asked about a way to restore deleted files after formatting a hard drive or a flash drive. Let’s talk about flash memory first. Most often, FAT32 is used as file system on such drives. When formatting to FAT32, a File Allocation Table is created early on the drive, containing information about individual files locations. The rest of the space is used by zeros and ones – bits which comprise the file’s content. A prominent characteristic of such file system is that the recorded files are highly fragmented: the start of the file may be in one spot on the storage, the middle part in the other, and the final part in yet another place. De-fragmentation utilities were highly popular a couple years ago, which tried to gather all parts of the file in one spot on the storage to reduce access time. So, if you delete a file, only the record about its whereabouts is deleted from the allocation table. The bits that form the file are still present on the storage, until parts of some other file overwrite the vacated spots. Full format deletes the allocation table and converts all ones on the drive to zeroes, making it completely blank. Special utilities can wipe the drive by rewriting the same spot with zeroes multiple times, ensuring it is deleted. On the contrary, quick format only deletes the allocation table, leaving the rest of the storage intact, meaning the files are still there. Recover utilities try to recreate the allocation table based on the file parts still present on the drive. If you copied something on the formatted drive and the new data was placed in the spots where old data was, some parts of the old files may get overwritten, and in this case the restored file will be corrupted – like those blank areas you may have on a recovered photo-file. Repairmen who offer data recovery mostly specialize in magnetic hard drives, simply because of the storage physical properties. Re-magnetizing is usually not overwhelming, and the old magnetic recording still shines through the new one for some time, meaning with special and highly expensive equipment, you may be able to recover the data from a formatted drive. Flash memory doesn’t have such properties. On a flash drive, a bit can only be zero or one, leaving no aftertaste. So your chances to restore a flash card or drive yourself or through a serviceman is virtually the same. If you performed a quick format and recorded nothing afterwards, chances are good to recover everything or almost everything. If you already recorded something new on the drive and the new files got placed on the spots where previous files were located, the restored files will be corrupted, and nothing can restore them, regardless of what the ads promise.

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