Mention SSDs and HDDs together and its bound to lead to transfer speeds, IOPS, power consumption, and the impending demise of HDDs. However, this article takes a different route—it's not about SSD vs. HDD; it's about data recoverability.
Undeleting data from a working HDD is easier than undeleting from a working SSD
The first category ( the easy category) of data recovery involves undeleting data, a seemingly uncomplicated task when the media itself is intact. With HDDs, especially CMR drives, undeleting data is typically straightforward. When you delete a file, the hard drive marks the space as "Free to write," allowing for data recovery until new data overwrites the designated space.
SSDs, however, operate differently. They can write in small pages but delete only large blocks. So every delete operation becomes a rewrite operation - all the valid data on that block is written to a new block, and the old block is deleted. To keep the SSD efficient and fast, the firmware will try to keep as many fresh blocks as possible. This is done with Garbage Collection which runs at the firware level , triggered by the TRIM command from the operating system.
So in short- HDDs retain deleted data until the space is needed for new data, while SSDs swiftly delete the data, making data recovery relatively easy on HDDs and significantly harder, sometimes even impossible, on SSDs.
Retreiving data from a failed HDD is tough, but it's even harder with a failed SSD.
Moving on to the second category of data recovery, dealing with hardware errors within the media itself presents a more intricate challenge. Repairing hard drives tends to be more feasible than repairing SSDs. HDD spare parts are readily available, given the dominance of three manufacturers—WD, Seagate, and Toshiba. Additionally, the magnetic retention of data on HDD platters ensures no leakage, a stark contrast to SSDs where charge gradually dissipates.
HDD repair can range from a straightforward daughter board replacement to the complex task of transferring platters to a new head. SSD repair, on the other hand, is notably challenging, if not entirely impossible. The tools required for SSD repair are considerably more expensive than the SSD itself. Even after repairing an SSD, it's not as simple as plugging it back into the system; specialized readers are necessary to extract data from each NAND cell, followed by meticulous work using software extractors. The complexities involved underscore the contrasting landscapes of HDD and SSD data recovery.