How well do you know your NAND?

Each of the various types of NAND flash have particular characteristics that influence which best suits an organization’s needs, so IT pros need to know the difference.

Jeff Rowe | Jul 09, 2018 12:00 am

It’s no secret that flash storage has revolutionized enterprise data storage in a short period of time. 

As tech writer Pedro Hernandez recently summed up the impact of flash, “compared to HDDs, SSDs  . . .  enable storage subsystems and arrays to provide blistering application performance and make short work out of business analytics and other workloads.”

But given that the underlying latest NAND architecture of SSDs can vary from model to model, it’s important for IT managers in healthcare and other sectors to understand that each of the various types of NAND flash – SLC, MLC, eMLC and TLC – have different characteristics that influence which is best for an organization’s storage needs.

As Hernandez explains, NAND flash is a type of non-volatile storage architecture used in SSDs and memory cards that “gets its name from the type of the logic gate (NOT-AND) used to determine how digital information is stored in a flash device's chips.”

From there, the nomenclature is pretty straightforward. Single-Level Cell SSDs (SLC) store one bit in each cell, “a design that yields enhanced endurance, accuracy and performance.” MLC designates multi-level cell architectures that can store two bits per cell. eMLC is a bit trickier, as it designates Enterprise Multi-Level Cells, “a hardier version of MLC NAND flash that somewhat bridges the performance and endurance gap between SLC and MLC.”

And then there’s Triple-Level Cell NAND flash, or TLC, which “stores three bits per cell and is typically used in consumer-grade electronics with comparatively low performance and endurance requirements. Best suited for read-heavy applications, TLC-based storage components were rarely, if ever, used in business environments but recent improvements in flash architectures, including 3D NAND (more on that later), and endurance-enhancing data placement and error correction techniques have earned the technology a place in read-intensive enterprise storage applications.”

As a rule of thumb, Hernandez says, “IT buyers looking for the highest performing SSD can expect to shell out much more for SLC than eMLC, MLC and TLC. But price isn't everything.

There are a lot of factors to consider when trying to the most bang for your storage buck. An SLC SSD makes sense for critical application workloads and 24/7 databases that demand fast, reliable performance. Of course, not every workload demands blistering speeds and price/performance considerations must also be taken into account.”

As with practically all facets of IT, NAND flash continues to evolve, so IT managers will naturally need to keep up with the changes in order if a flash drive is suitable for an intended workload or use case.


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