▷ Types of nand memory in ssd: slc, mlc, tlc and qlc

One of the most important components of an SSD is the NAND memory that it includes inside, on which the performance and characteristics of the SSD largely depend. In this article, we review the four main types of NAND memory that we can find on SSDs.

Index of contents

SLC, MLC, TLC and QLC memories

NAND flash memory is made up of many cells that contain bits, and those bits are turned on or off through an electrical charge. The way those on / off cells are organized represents the data stored on the SSD. The number of bits in those cells also determines the NAND naming, for example, Single Level Cell Flash (SLC) contains a single bit in each cell.

The reason why SLC is only available at lower capacities is due to the large size of the NAND flash on the printed circuit board (PCB). Don't forget that the circuit board must have the controller, the cached DDR memory and the NAND memory where user data will be stored. MLC memory doubles the number of bits per cell, while TLC triples it, and QLC multiplies it by four.

There are particular reasons why manufacturers build flash memory with just one bit per cell like SLC. SLC has the advantage of being the fastest and most durable memory, but it has the drawbacks of being more expensive and is not available in higher storage capacities. That's why SLC is preferred for heavy business use.

MLC, TLC, and QLC memories are cheaper to produce compared to SLC and are available in larger storage capacities, but have relatively shorter lifetimes and slower read / write speeds. MLC and TLC are preferred for everyday consumer use.

Here we review the most important characteristics of the four main types of NAND flash memory:

SLC (single level cell)

The NAND SLC is named for its unique bit that can be turned on or off when loaded. This type of NAND has the advantage of being the most accurate when reading and writing data, and also has the advantage of lasting the longest cycles of reading and writing data. The program's read / write life cycle is expected to be between 90, 000 and 100, 000. This type of NAND has performed exceptionally well in the business market due to its useful life, accuracy, and overall performance. You won't see too many home computers with this type of NAND due to its high cost and low storage capacity.

Pros:

• It has the longest lifespan and charge cycles over any other type of flash. Smaller and more reliable room for read / write error. It can operate in a wider temperature range.

Cons:

• The most expensive type of NAND flash on the market, often only available in smaller capacities.

Recommended for:

Industrial use and workloads that require intense read / write cycles, such as servers.

MLC (Multiple Level Cell)

MLC as its name suggests stores multiple bits of data in a cell. The big advantage of this is the lower manufacturing cost compared to manufacturing NAND SLC memory. The lower cost in flash production is generally passed on to the consumer, and for that reason it is very popular with many brands. NAND MLC is preferred for consumer SSDs because of its lower costs, but data read / write life is shorter compared to SLC.

Pros:

• Lower production costs are passed on to the consumer. It is more reliable than TLC flash.

Cons:

• It is not as durable and reliable as a company SLC or SSD.

Recommended for:

Everyday use of the consumer, gamers and enthusiasts.

TLC (triple cell level)

By storing 3 bits per cell, TLC is a very cheap way to manufacture NAND. The biggest disadvantage of this type of flash is that it is only suitable for consumer use and could not meet the standards for industrial use. Read / write lifecycles are considerably shorter, 3, 000 to 5, 000 cycles per cell.

Pros:

• Cheaper to make, which in turn leads to a cheaper SSD to market.

Cons:

• Cells will survive considerably fewer read / write cycles compared to MLC NAND. This means that TLC flash is good for consumer use only.

Recommended for:

Daily consumer use, web / email machines, netbooks and tablets.

QLC (quadruple cell level)

This type of memory takes a new step by storing 4 bits per cell, making it the memory with the highest storage density, and the one that makes it possible to manufacture the cheapest SSDs. The downside is that its lifespan is even shorter than that of TLC. This type of memory is very recent, so there are hardly any devices that use it.

Pros:

• The cheapest memory to make, which in turn leads to a cheaper SSD.

Cons:

• Cells will survive even fewer read / write cycles compared to TLC NAND.

Recommended for:

Daily consumer use, web / email machines, netbooks and tablets.

We recommend reading the following tutorials:

• Best SSD on the market

This ends our article on NAND memory types in SSD. Viewing from the most complete as the SLC to the least durable as TLC or QLC.