The pros and cons of QLC NAND FLASH

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The pros and cons of QLC NAND FLASH

Flash storage has come a long way. We’ve gone from old-fashioned spinning hard drives to the early days of SSDs, which brought about significant improvements to data storage.

NAND Flash is a type of non-volatile memory which has continued to evolve since landing on the market in the late 1980s.

SLC stands for Single-Level Cell, where there is one bit per cell. It was the first type of flash technology, and was expensive with limited capacity when it was introduced.

There was then the transition to MLC (Multi-Level Cell), which allowed for two bits per cell, and 100% increase in density from SLC. This was a milestone that helped to make flash memory more affordable and accelerated its adoption.

TLC (Triple-Level Cell) then offered a 50% increase over MLC, going from two to three bits per cell. This advancement saw flash memory adopted for mainstream IT usage as it was affordable, reliable, and performant.

QLC stands for Quad-Level Cell, and is the latest evolutionary step in flash storage. QLC NAND uses four-bit layers per cell for 16 possible binary values – twice as many as TLC.



While QLC NAND is faster and can store more than TLC NAND, there is a trade off regarding its ability to withstand heavy read/write cycles.

Advantages of using QLC NAND FLASH
QLC SSDs will be welcomed in enterprise environments.The higher density means smaller, higher-capacity devices, which is useful for IT departments as it saves on rack space, especially in comparison to HDDs.

With a lower read latency, QLC is better for read-intensive operations. It will be used in applications such as Big Data, AI, machine learning and content delivery.

As always, more storage at better cost efficiency is always welcome. The lower read latency means quicker access to data. QLC NAND also has a lower power consumption, which will help improve the battery life of the devices.

Disadvantages of using QLC NAND FLASH
Chips-based NAND flash has an endurance rating which is based on the finite amount of times data can be written before it fails. This is referred to as a Program-Erase Cycle (P/E Cycle) and is the primary trade-off of using QLC NAND.

SLC offers up to 100,000 P/E cycles, with MLC at 10,000 P/E cycles, with TLC reducing this further to 3,000 P/E cycles.

QLC offers less still – just 1,000 P/E cycles. This looks like a dramatic decrease, but it is still an acceptable rating for consumer or professional use which is not reliant on write-heavy applications.

The impact of QLC NAND FLASH on SSDs
NAND flash is an extremely prolific technology. It’s an integral part of all smartphones, tablets, and laptop computers, and is almost certainly going to play a big role in the next generation of data centers, where storage densities are soaring and energy consumption is a major concern.

QLC flash storage is scalable, which means there could be a huge increase in storage capacity in the next decade. It’s also non-volatile, which means data can be stored for a very long time. But traditional NAND flash technology, is getting a little bit old and is not as capable of handling the huge information from new technologies like 5G and WIFI 6.

If you are considering a QLC NAND flash chip, you should understand two important characteristics of the technology.

First, QLC NAND flash is more expensive per bit than MLC NAND flash, and vendors have thus far been unwilling to pass these higher costs onto their customers. But its strengths finally make a case for replacing mechanical disks with much faster and bigger solid-state drives.

Second, QLC NAND flash has a worse endurance rating than MLC NAND flash. Currently, the TLC SSDs remain the better choice in write-heavy applications in terms of balancing endurance with cost.