SSD 101: Guide to Solid-State Drive

A logical controller interface through which the solid-state device communicates to a computer via a physical connection from the SSD’s M.2 or U.2 to the PCI Express slot on that computer’s motherboard is NVM Express.

NVM Express is similar to the USB connector on most portable hard drives. It was designed to maximize the bandwidth and performance of solid-state storage devices. This interface allows levels of parallelism found in modern SSDs to be fully utilized by the host hardware and software. As a result, NVM Express reduces I/O overhead and brings various performance improvements compared to previous logical device interfaces, including multiple, long command queues and reduced latency.

PCI Express (PCIe) is a high-speed serial connection on a computer that acts more like a network than a traditional bus. A bus is a communication system that transfers data between components inside a computer, or between different computers. Instead of one bus that handles data from multiple sources, PCI Express (PCIe) uses a switch that controls several point-to-point serial connections. These connections lead to the devices where the data is needed. Every device has its own connection, so there is no sharing of bandwidth like what occurs on a normal bus. PCle has other advances over the older standards, including higher throughput, smaller physical size, more detailed error detecting and reporting mechanisms along with greater support for I/O virtualization.

The difference in these terms is somewhat self-explanatory. With a single-level cell (SLC), only one piece of information (one bit) is contained within a storage cell. Multi-Level cells (MLC) can hold two pieces (bits) of information, Triple-Level Cells TLCs can hold three bits of information per cell, and Quad-Level Cells (QLCs) can store four bits per cell.

As stated by TechTerms.com, “NAND is not an acronym. Instead, the term is short for ‘NOT AND,’ a boolean operator and logic gate. The NAND operator produces a FALSE value only if both values of its two inputs are TRUE. It may be contrasted with the NOR operator, which only produces a TRUE value if both inputs are FALSE.”

The process through which the controller balances the writing and erasing of data across the storage area of an SSD is wear leveling. The idea is similar to rotating the tires on your car and including the spare tire in the rotation to spread the wear evenly on all tires. With an SSD, the usage is spread across all available cells to prolong the operating life of the media.

As stated by TechTerms.com, “NAND is not an acronym. Instead, the term is short for ‘NOT AND,’ a boolean operator and logic gate. The NAND operator produces a FALSE value only if both values of its two inputs are TRUE. It may be contrasted with the NOR operator, which only produces a TRUE value if both inputs are FALSE.”

U.2 is the upgraded external physical cable interface, formerly known as Sata Express, for connecting external storage devices to the PCI Express port on the backplane of the computer.

P/E Cycle, or Program Erase Cycle, is a way to measure how many times the storage areas of a solid-state drive can be written to, deleted, and then re-used.