Choosing storage: NVMe vs SATA SSDs, PCIe generations and capacity

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Storage choices have become simpler now that solid state drives are standard, but the labels on the box can still mislead. Two drives that look identical can perform very differently, and the fastest drive is often not the best buy. This guide covers the formats, PCIe generations and how much space you need.

The formats

M.2 NVMe SSDs

The usual choice for a new build. These small sticks plug straight into the motherboard and use PCIe lanes, giving far higher speeds than older drives. Most new boards have at least two M.2 slots.

M.2 SATA SSDs

They look like NVMe drives but use the older SATA interface and are limited to SATA speeds. Not every M.2 slot supports SATA, so check the board manual before buying one. For a new build, an NVMe drive is usually the better buy.

2.5-inch SATA SSDs

These connect with a SATA data cable and a power cable. They are limited to roughly 550MB/s but still feel quick for everyday use and are a good way to reuse a drive from an older PC.

Hard drives

Mechanical hard drives are slow but offer large capacities cheaply. They suit bulk storage such as media libraries and backups, not the operating system or games.

PCIe generations

NVMe drives are sold as PCIe 3.0, 4.0 or 5.0, with each generation roughly doubling the maximum transfer rate. Drives and slots are backwards and forwards compatible, running at the speed of the slower of the two.

PCIe 4.0 drives are the sweet spot for most builds, with sequential speeds of up to around 7,000MB/s on good models.
PCIe 5.0 drives can be much faster in sequential transfers, but they run hotter and usually need a substantial heatsink. In gaming and everyday use, the difference over a good PCIe 4.0 drive is often hard to notice.
PCIe 3.0 drives are still fine for secondary storage.

Check which M.2 slot runs at which speed. Usually only one or two slots are connected directly to the CPU, while others go through the chipset. On some boards, using certain M.2 slots disables SATA ports or reduces the lanes for the graphics card slot, which the manual will explain.

What matters beyond headline speed

Random performance and consistency affect how fast a system feels more than the large sequential numbers printed on the box.
DRAM cache or HMB. Better drives have their own DRAM cache. Many cheaper drives are DRAM-less and use a small slice of system memory instead, called Host Memory Buffer, which works well for most home use.
Endurance. Drives list a TBW (terabytes written) rating and a warranty period. For gaming and everyday use, most people never come close to the rating.
Heat. Use the motherboard's M.2 heatsink if it has one, particularly for PCIe 4.0 and 5.0 drives, and check it will not clash with a large graphics card or cooler.

How much capacity?

500GB is tight today once the operating system, updates and a few apps are installed.
1TB is a sensible minimum for a general-use PC or a light gaming PC.
2TB or more suits gaming, as many modern games take up a large amount of space each.
Leave free space. SSDs work best when they are not completely full, so plan for some headroom.

A common approach is one fast NVMe drive for Windows, apps and favourite games, plus a second larger drive for the game library or media. A second M.2 slot makes adding storage later easy.

Installing and setting up

Fit the drive in the main M.2 slot for the operating system, using the standoff and screw or clip supplied with the board.
Remove the protective film from the heatsink's thermal pad before fitting it.
Install Windows on the main drive; additional drives may need initialising in Disk Management before they appear.
Check the drive's health with the maker's software, which also offers firmware updates.

Which drive setup are you running, and would you change it? Share your experience in the comments.