SSDs use non-volatile, solid-state storage media, such as flash media, to persistently store large amounts of data. SSDs can operate in a manner similar to conventional hard disk drives (HDDs), but lack the motor, magnetic disc, read head, and other moving components of HDDs. The lack of moving parts makes SSDs more rugged than HDDs. For example, when an HDD is dropped or shaken, the read head can collide with and sometimes damage the rotating magnetic disc. Additionally, SSDs have faster read/write speeds than HDDs, and they make virtually no noise.
Another advantage of the solid state media of SSDs is that it gives an SSD greater extensibility than an HDD. For example, HDDs typically require a data file to be stored in contiguous memory blocks because the read head needs to read the magnetic media in one continuous motion. By contrast, SSDs can store memory blocks for any one file at arbitrary locations in the solid state media. Additionally, some SSDs can dynamically reduce, or “trim,” memory capacity in exchange for a faster read/write speed.
Some extensible features include restricted commands such as commands for electrically testing the SSD during production or in the field. These commands are typically locked out via password protection to prevent novice or other users from executing them because, in certain cases, the restricted commands may irreversibly alter the SSD and even render it inoperable. For example, some restricted commands can erase or wipe out critical portions of the SSD firmware. One challenge with conventional password protection, however, is that it can be circumvented once a password becomes public knowledge.