In plain words
Buying an SSD is like buying a tyre: first you need the right size for the rim (the form factor), then the right type for the car (SATA or NVMe), and only then do you compare performance. The fastest tyre in the world is useless if it does not fit in the wheel arch.
Replacing a hard drive with an SSD is the most effective upgrade for an old computer: startup in a few seconds, apps that open instantly. You still need to buy a compatible model.
1. The physical form factor: what your machine accepts
| Form factor | What it looks like | Where you find it |
|---|---|---|
| 2.5-inch SATA | Rectangular case the size of a thick credit card | Older laptops, desktop PCs, a drop-in replacement for a 2.5" hard drive |
| M.2 | Thin stick, no case, screwed onto the motherboard | Nearly every recent PC |
| mSATA | Older small stick | Some laptops from the 2010s |
An M.2 drive's length is in its name: 2280 means 22 mm wide and 80 mm long. It is the most common size; some thin laptops need 2230 or 2242.
Check before you buy
Read the manual or specification sheet of your motherboard or laptop: number of slots, accepted form factor and supported protocol. For a laptop, the exact model reference (under the machine or in the system information) is enough to find this.
2. The protocol: SATA or NVMe
An M.2 slot can work in SATA or NVMe (PCIe) mode, and the two are not interchangeable everywhere. Visual clue: an M.2 NVMe SSD has a single notch (M key), an M.2 SATA drive usually has two (B and M keys); but only the slot's specification sheet is authoritative.
| Type | Approximate maximum throughput |
|---|---|
| SATA (2.5" or M.2) | 550 MB/s |
| NVMe PCIe 3.0 | 3,500 MB/s |
| NVMe PCIe 4.0 | 7,000 MB/s |
| NVMe PCIe 5.0 | 14,000 MB/s |
A PCIe 4.0 SSD works in a PCIe 3.0 slot, but at 3.0 speed. For office use, the difference between SATA and NVMe is barely noticeable; it matters for video, large files and games.
3. The specifications that really matter
- Memory type: TLC offers the best compromise. QLC, cheaper, wears out faster and slows down sharply during long copies once its cache is full. It suits data storage, less so the system drive.
- DRAM cache: models with DRAM hold their performance better. Without DRAM, NVMe drives use part of the PC's memory (HMB): fine for everyday use.
- Endurance (TBW): the total volume that can be written, in terabytes. A good 1 TB model is rated at about 600 TB: at 50 GB written per day, that is more than 30 years of home use.
- Warranty: 5 years on good models, a sign of the manufacturer's confidence.
Warning
Beware of unknown-brand SSDs at very low prices on marketplaces: the real capacity is sometimes lower than advertised, and the lifespan is unpredictable. Stick with recognised memory manufacturers.
4. Capacity
| Use | Recommended capacity |
|---|---|
| Office work, browsing | 500 GB |
| General use, photos | 1 TB |
| Gaming, video, creative work | 2 TB and more |
A nearly full SSD slows down: keep a margin of at least 15 to 20%.
5. What about an external SSD?
Look at the connection: a fast external SSD is useless if the computer's port is slow.
| Connection | Approximate real throughput |
|---|---|
| USB 3.2 Gen 1 (5 Gbps) | about 450 MB/s |
| USB 3.2 Gen 2 (10 Gbps) | about 1,000 MB/s |
| USB4 / Thunderbolt | 2,000 to 4,000 MB/s and more |
6. Moving to the new SSD
Two options:
- Clean reinstall of the system on the SSD: the most reliable solution, and a chance to start fresh.
- Cloning the old drive to the new one, with a tool such as Clonezilla (free software) or the software often supplied by the SSD manufacturer.
Either way, make a full backup before you start.