SSDs have become one of the most popular technologies over the last decade thanks to the incredible performance boost they offer for desktop and business computers compared to traditional hard drives. They're also lighter and consume less power, which improves laptop battery life, and since they contain no moving parts, dropping your device on a hard surface won't damage the data on it. HDD. . SSDs are now a standard feature on most new consumer PCs. But the technology has some unique quirks that mean it needs to be designed, used, and configured in a slightly different way. SSDs have two main components: a controller, which is a small processor with its own memory, and an array of several million flash memory cells that are used to store data. Flash memory cells are non-volatile silicon chips (meaning they retain data when powered off, unlike system memory) and can be erased and written multiple times. Each cell can contain data in a floating gate, written with voltages. Featuring self-encrypting drives, designed to add a strong layer of security to data stored on an SSD, the controller also contains a dedicated processor to encrypt and decrypt data as it is read from flash memory. Everything you own today that is used for data storage is likely to contain NAND Flash; its use has grown exponentially over the years with petabytes (ie one million gigabytes) of product shipped over the past decade. NAND can be found all around us today: the smartphone you own, a web host's server, the computer in your office, and even complex medical equipment can all have NAND on it. Not all NAND is created equal, understanding the difference between NAND flash types is an important task, but one that is often overlooked by consumers. Different types of NAND have different characteristics, which has major implications in terms of performance, endurance, reliability, and cost.
The limits of flash memory
The first limitation is that, in general, flash storage is still more expensive than hard drives of the same capacity. Although SSD prices have fallen staggeringly over the past decade, in part due to increased manufacturing efficiencies with lower overheads and explosive growth in demand, there is still a need to reduce the cost per gigabyte of flash storage. The second problem is that flash memory has a limited lifespan. Evaluated in P/E (Program-Erase) cycles, each cell on an SSD can only be written to a certain number of times before it no longer contains an electrical charge. There is currently no way to completely avoid this problem with any type of flash memory.
SLC and MLC NAND
Faced with these issues, engineers found a clever way to get more data storage capacity out of the same amount of NAND flash in an SSD by increasing the number of data bits each cell can hold. The downside is that with each cell that holds more data, the drive's endurance drops, reducing the number of P/E cycles an SSD is rated for. NAND Flash, which can only hold one bit of data per cell, with two binary values, 0 or 1, is called SLC. But this NAND is so expensive per gigabyte that SLC SSDs are prohibitively expensive and unsuitable for use in consumer PCs and laptops. But SLC NAND offers the best possible endurance, with up to 100.000 P/E cycles. MLC NAND uses two data bits per cell, with 4 possible binary values. When SSDs began to take off a decade ago, it was thanks to MLC NAND flash memory that allowed useful SSD capacities in a standard desktop or laptop computer to finally become affordable. But increasing storage capacity reduces the SSD's endurance to 10,000 P/E cycles. While this reduced longevity seems like a big drop, you're unlikely to "wear out" an MLC SSD unless you're constantly writing to it. In most typical home setups, including even high-end gaming, design, and content creation workstations, there are few use cases where data is constantly being written to a drive. Enterprise and data center usage is slightly different, which is one reason a typical enterprise SSD is configured differently than a consumer drive, but here too, the endurance of an MLC player is never it should become a problem, even for long periods of time. .
TLC NAND
The MLC concept has been so successful that the obvious next step is to use even more data bits per cell. 3D TLC NAND Flash uses three bits per cell, for 8 possible binary values, providing another huge capacity improvement / cost reduction. This technology has helped make SSDs mainstream, affordable enough to be used in any computer at capacity levels useful for most applications. As of 2021, TLC has become the predominant technology in all consumer SSDs, used in high-performance drives for servers, PC gaming, and even the most demanding client-side computing, as well as in high-end SSDs. affordable entry-level devices intended for more general use. But with TLC technology, endurance is reduced even further, to just 3000 P/E cycles. It may seem like a worrying reduction, but even with reduced endurance, an average user will have a hard time telling a difference between an MLC and a TLC SSD. . Most software applications spend more time reading data from a disk than writing to it. Basic computer tasks, such as browsing the web, sending email, and word processing, write virtually no data to disk. Games and apps are usually only installed once and never overwrite a large amount of data again. Even high-level tasks that involve handling large files like video editing and graphic design won't spend all day writing large files, but the writes are often sporadic. For almost everyone, a TLC SSD is a great option, it will perform to high standards and cost much less than a high-end MLC drive. It has now replaced MLC as the dominant SSD technology.
QLC NAND
The next step in SSD technology is QLC: four layers of bits per cell, for 16 possible binary values. This allows for another surprising increase in capacity and a reduction in costs. It also means reduced endurance, at just 1000 P / E cycles. QLC is the most affordable NAND technology and QLC SSDs are the cheapest drives you can buy. Despite further reductions in endurance, QLC SSDs have already become commonplace.
What is 3D NAND?
As SSD technology evolved, engineers encountered another problem in scaling regular 2D NAND to achieve higher densities at lower cost. In 2D NAND, the cells that store the data are placed horizontally, next to each other. This means that the amount of space cells can be placed in is limited and trying to make cells smaller reduces their reliability. This limitation was overcome by stacking cells vertically and horizontally, allowing for greater storage capacity, improved endurance, and lower power consumption. 3D NAND is now used in conjunction with TLC technology and QLC technology in most high-end drives to achieve the best combination of strength, capacity, and cost.