Hard disk drives have been around for decades, so it’s no wonder the data recovery industry has had to the time to perfect its tools for retrieving lost data from the magnetic storage devices. Solid-state drives are newer technology, however, a superior alternative that offer many benefits over HDDs such as read-write speeds, shock resistance, and overall durability. But SSDs do have some limitations, in particular the lifecycle, which is limited to roughly 100,000 read/writes before the drive completely wears out.
Storage and Data Recovery on an HDD
To visualize how data storage and erasure works on both HDDs and SSDs, let's compare the storage medium to a library. When the user saves data to a drive, it's like filling the empty shelves of a library with books. The librarian (or file system) has a catalog of the entries and where they are stored, so when someone (the user) asks for a book (a file), the librarian checks the catalog and directs the reader to its ‘address’ in the system.
When a user deletes a file, the ‘librarian’ marks the ‘book’ as removable and updates the catalog by removing any references to that entry. However, the removal only takes place when a new entry arrives and the librarian needs the free space to place it on the shelves.
This is why data recovery is possible on hard disk drives. The data is actually still there on the medium, even though it is hidden from the user. A data recovery app checks the catalog, and the ‘old address’ to find any hidden – or ‘removed’ – data.
Storage and Data Recovery on an SSD
While saving the data on an SSD is somewhat similar to what happens on an HDD, the main difference between the two storage mediums is what happens when erasing data. With a solid-state drive the metaphorical librarian can only place a new book on the shelf if it is empty or all the books are removed from it. To do so, any books that are marked as no longer needed are put through a shredder to completely destroy them, allowing for the new books and to be put on the empty shelf. Also, to keep an up-to-date catalog and avoid confusion, the librarian then burns the old book catalog.
It is the job of the TRIM command to destroy the files on an SSD when they are deleted, which is meant to equalize the wear level of all the drive’s storage blocks (where data is written). It eliminates the risk of writing data too many times to the smallest storage sector since if one area is repeatedly used then it will become more and more worn and, eventually, become useless. TRIM addresses this issue by instructing the operating system to erase the whole page to ensure gradual wear.
Since the TRIM command erases everything in the block, data is impossible to retrieve via software because it has already been overwritten. However, some data recovery experts have found ways to recover data knowing that TRIM doesn’t engage in certain setups, such as via a secondary SATA connection or USB. If you really hope to recover data from an SSD, then you need to take the hardware to a lab, where experts will perform various actions to get the data back for you.
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