A NAND and V-NAND are both types of flash memory which is a class of non-volatile memory that retains data even in the absence of an electrical current.
Flash memory is very portable and combined with its other characteristics of durability and speed, it is perfect for storing mass data as required of an SSD or USB flash drive. Flash memory is made up of an array of cells which record 1 or several bits (0 or 1). Each cell comprises floating gate transistors that trap an electrical charge (indicating the 1or 0). Single-level cells (SLC) store one bit, multi-level cells (MLC) store two, triple-level cells (TLC) store three and quad-level cells (QLC) store four bits. With the increase in levels there is a decrease in cost, but also a decrease in the number of program/erase cycles.

There are two types of flash memory: NOR and NAND referring to the logic gates used in the memory cells. NOR based flash has the advantages of being able to read, write and erase each byte individually and has faster read speeds than NAND. However it is more expensive and around 60% less dense than the NAND equivalent. NOR memory is mainly found embedded in devices such as mobile phones and small appliances.

NAND technology is currently the prime flash memory type for SSDs. Hundreds to thousands of cells are arranged on pages and there are multiple pages on a single block (128KB+). A chip consists of multiple blocks. A degree of block management is required for writing and erasing data, and data can only be read on a page basis, making it unsuitable for the byte level random access required of ROM, but great for sequential access. NAND has better endurance than NOR (reportedly up to 10 times) and faster write and erase speeds thanks to the way data is organised in blocks. And of course the other significant benefit of this block architecture is that NAND is relatively cheap to manufacture.

V-NAND, or 3D V-NAND is the latest technology in the flash memory world. This is where planar NAND (single planes of NAND cells) are stacked vertically, giving the ‘V’ in V-NAND. Due to the change in vertical arrangement of cells these SSDs have better capacities at lower production costs, half the power requirements, twice the speed and ten times the longevity of planar NAND. The enhanced capacity has allowed Samsung to bring the world’s first 2TB SSD to the consumer market in the form of the SATA-based Samsung 850 Pro

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