SSD Specs in Plain English

Sustained Speed Rating

This is the rating you'll see on my listings: High, Medium, or Low. It tells you how a drive performs under real workloads rather than what it can do for a short moment, or with a single file.

Why does this matter? Because the headline speed on the box only tells you how fast the drive bursts. It doesn't represent how it behaves a few solid minutes into a large install or file transfer. It's just what it is technically capable of.

NAND Type — SLC / MLC / TLC / QLC

NAND is the actual memory that stores your data. The letters refer to how many bits are crammed into each memory cell.

• SLC (1 bit) — Extremely fast and durable. Only used in enterprise drives. Not relevant to consumer purchases.
• MLC (2 bits) — Largely discontinued for consumer use.
• TLC (3 bits) — The standard for good consumer SSDs. Fast, durable enough for years of heavy use, reasonably priced.
• QLC (4 bits) — Cheaper to make, cheaper to buy. Slower under sustained writes and wears out faster. The trade-off is fine for a secondary drive where you mostly just read.

More bits per cell = cheaper, denser, but slower and shorter-lived. TLC is the sweet spot; QLC makes sense when you want a lot of storage for as little money as possible and aren't writing to it constantly.

DRAM Cache

SSDs need an index, which is like a map of where every file actually lives on the drive. Reading and updating that map constantly is one of the most performance-critical things the controller does.

A DRAM cache is a small chip of fast volatile memory (similar to your system RAM or GPU's VRAM) that lives on the SSD itself. Keeping the map in DRAM means the controller can look things up in microseconds, consistently, without slowing down under pressure.

Drives without dedicated DRAM use HMB (Host Memory Buffer) instead — they borrow a small slice of your system RAM to do the same job. This works well enough for most everyday tasks, but adds a bit of latency, since lookups have to leave the drive and travel across the bus to reach your system RAM. On these scales, the physical distance between the RAM module on the motherboard and your drive actually matters. It's why you always see RAM sat right up next to the CPU socket.

Does it matter? For light-to-moderate use, HMB is genuinely fine. Under heavy mixed workloads, like lots of simultaneous reads and writes, a DRAM-equipped drive stays more consistent.

NVMe vs SATA

The interface is how the SSD connects to your motherboard and how fast data can actually travel between them.

• SATA — The older standard. Maxes out around 550 MB/s. Still solid, just not that special these days. It's also why basically every SATA SSD you see advertises something around 550 MB/s — that's just the limit of standard SATA.
• NVMe — The modern standard. Plugs directly into an M.2 slot on the motherboard. You can also find ones that are built onto a PCB and slot into a PCIe slot like a GPU. Much faster than SATA, and built specifically for flash storage rather than repurposed from hard drive technology.

NVMe drives also come in different PCIe generations (Gen 3, Gen 4, Gen 5). Gen 4 is the current mainstream. Gen 5 exists but is expensive and overkill for gaming and desktop use. Gen 3 is still perfectly fast for most people.

Does it matter? Yes. NVMe vs SATA is a meaningful difference. Gen 3 vs Gen 4? Not so much for most of us.

TBW (Endurance)

Terabytes Written. This is the total amount of data the manufacturer rates the drive to handle before reliability is no longer guaranteed.

A typical 1TB TLC drive is rated around 600 TBW. If you write 50GB a day (a heavy desktop user), that's over 30 years of rated life. Most drives outlive their TBW rating. This spec mainly matters for NAS boxes, databases, or anything writing data continuously around the clock.

Important? Rarely for consumer use. Worth checking if you're running a home server or doing anything unusually write-intensive.