Two SSDs can have the same capacity and similar headline speeds yet behave very differently in real use — and the reason is usually the type of NAND flash inside: QLC, TLC, or MLC. This determines the drive's endurance (how much you can write to it over its life) and how it holds up under sustained writes once its fast cache is exhausted. The cheapest drives often use QLC and hide its weakness behind an SLC cache that masks the problem — until it doesn't. This guide explains the difference so you buy a drive that lasts.
It complements our NVMe SSD buying guide and the DRAM-less trap.
The Three NAND Types
- MLC (2 bits per cell): the oldest of these and the most durable, with high endurance. Rare and expensive in consumer drives now — mostly found in older or premium/enterprise units.
- TLC (3 bits per cell): the mainstream sweet spot — a good balance of endurance, performance, and price. Most quality consumer SSDs use TLC, and it's what you should aim for.
- QLC (4 bits per cell): cheapest and densest, but with lower endurance and slower sustained writes. Fine for light use and bulk storage; a poorer choice for heavy writing.
More bits per cell means cheaper and denser, but lower endurance and slower sustained performance — that's the core tradeoff.
How the SLC Cache Hides the Problem
Here's the trick that fools benchmarks. Most drives (especially QLC ones) use a portion of their NAND as a fast "SLC cache" that absorbs writes at high speed. Short transfers and benchmarks fit in this cache, so the drive looks fast. But during a large sustained write — copying a big video project, for instance — the cache fills, and the drive falls back to its true (much slower on QLC) native speed. So a QLC drive can post great benchmark numbers yet crawl during the real heavy task. See sustained write performance.
Which to Buy in Nigeria
- TLC for your main drive: the right choice for a boot/working drive — good endurance and sustained speed at a sensible price. Aim for TLC by default.
- QLC only for light bulk storage: acceptable as a secondary drive for media you mostly read, on a tight budget — but not for heavy writing or as a video scratch drive.
- MLC isn't worth hunting for in consumer drives now — a quality TLC drive is the practical best buy.
The Nigeria Tax
Because you can't easily replace a worn or disappointing drive here, buying the right NAND the first time matters. A quality TLC drive is the safe, lasting choice for a main drive; resist a QLC bargain for anything write-heavy, since its slow sustained writes and lower endurance will frustrate you under real load. Manufacturers don't always advertise the NAND type prominently — check reviews to confirm a drive is TLC before buying it as your primary. Put a good TLC drive in a build like our ₦1M guide.
Frequently Asked Questions
What's the difference between QLC, TLC, and MLC? They're NAND flash types storing 4, 3, and 2 bits per cell respectively. More bits means cheaper and denser but lower endurance and slower sustained writes. TLC is the mainstream sweet spot; QLC is cheapest but weaker; MLC is durable but rare now.
Why does a cheap SSD slow down during big transfers? Most drives use an SLC cache that absorbs writes at high speed, so benchmarks and short transfers look fast. During large sustained writes the cache fills and the drive drops to its true speed — much slower on QLC.
Which NAND should I buy? TLC for your main drive — good endurance and sustained speed at a sensible price. QLC only for light bulk/secondary storage on a budget, never for write-heavy work. Check reviews to confirm the NAND type.
The One Thing to Remember
The NAND type decides an SSD's endurance and sustained speed: TLC is the sweet spot for a main drive, QLC is cheapest but weak under heavy writing (and hides it behind a cache that fools benchmarks), and MLC is durable but rare. In Nigeria, where replacing a drive is a hassle, buy a quality TLC drive for your primary storage and reserve QLC for light bulk use only.
Picking an SSD? Configure a build online → or talk to our team → and we'll spec a quality TLC drive that lasts — not a QLC bargain that disappoints under load.