SSDs are expensive but not necessarily fast: the interface protocol and main control are the key

Solid-state drives (SSDs) are the most obvious upgrade direction to speed up computers, but the product parameters on the market are confusing—some 1TB cost less than 300 yuan, and some cost 800 yuan for the same capacity. What’s the difference? Most consumers can't tell the difference, and the pitfalls are mainly concentrated in the three areas of interface, protocol and cache.

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Interface type: determines the physical installation method

There are three common interface forms of SSD:

Interface	Typical specifications	Connection method
SATA	2.5-inch, M.2 2280 (using SATA protocol)	Motherboard SATA interface or M.2 SATA
M.2 NVMe	M.2 slot, PCIe channel	Direct plug-in motherboard M.2 slot
PCIe direct plug	graphics expansion card	PCIe x4 slot, server/fever oriented

The first two are commonly used at the consumer level:

• SATA SSD (M.2 or 2.5 inches): The upper limit of reading speed is about 550MB/s, and the writing speed is about 520MB/s. It is cheap and suitable for upgrading old machines.
• NVMe M.2 SSD: read speed 3000–7000+ MB/s, 5–10 times faster than SATA, suitable for new platforms

Determine whether M.2 is SATA or NVMe:

• Look at the location of the golden finger notch: SATA only has one notch (B+M key); NVMe usually only has one notch for M key.
• Look at the price: SATA with the same capacity is cheaper
• Look at the motherboard specifications: The M.2 slot states whether it supports NVMe, SATA or is compatible.

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Protocol version: PCIe 3.0 vs 4.0 vs 5.0

The protocol determines the total bandwidth of the data transmission channel:

Protocol	Theoretical maximum bandwidth (x4 channels)	Sequential reading speed upper limit
PCIe 3.0 NVMe	~4 GB/s	~3500 MB/s
PCIe 4.0 NVMe	~8 GB/s	~7000 MB/s
PCIe 5.0 NVMe	~16 GB/s	~14000+ MB/s

Actual usage perception:

Scenario	SATA	PCIe 3.0 NVMe	PCIe 4.0 NVMe
System startup	About 12–15 seconds	About 10–12 seconds	About 9–11 seconds
Large game loading	Significantly slow	Fast	Slightly faster
Large file transfer (100GB+)	Slow	Fast	Significantly fast
Ordinary daily use	No difference can be felt	No difference can be felt	No difference can be felt

Conclusion: PCIe 3.0 is sufficient for daily office use, gamers recommend PCIe 4.0, and creative workers (video editing/large file transfer) consider PCIe 4.0 or 5.0.

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With cache vs without cache: affects sustained writing speed

DRAM cache (independent cache):

• An independent DRAM chip is used as a buffer, and the main control is fast and stable when reading and writing frequent small blocks of data.
• Not easy to slow down when writing a large amount of data
• higher price

No cache (HMB or pure no cache):

• HMB (Host Memory Buffer): Borrowing system memory for buffering, which is better than pure no cache, but continuous writing will still slow down
• Pure no cache: cheap, speed will drop from 3000MB/s to about 800MB/s after continuous writing of 10–30GB
• Suitable for scenarios that do not require high speed (light office, archive disk)

Which scenario requires caching:

• System disk: DRAM cache is strongly recommended
• Video editing work disk: cached
• Pure data backup/archive disk: no cache + large capacity and high cost performance

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Main control: determines stability and lifespan

The main control is the "CPU" of the SSD and is responsible for scheduling read and write, wear leveling, error correction and other tasks.

Key Parameters:

• TBW (total write volume): represents the total amount of data that can be written to the hard drive during the warranty period. 1TB capacity usually has a TBW of 300–600TB.
• MTBF (Mean Time Between Failures): Usually marked as 1.5 million hours, this is a theoretical value, for reference only
• Disk drop problem: Some low-end controllers will feign death (disk disappears) when exposed to high temperatures or when writing a large amount of data, seriously affecting use.

TBW Reference:

Usage intensity	Daily writes	Recommended TBW (1TB)
Light (office browsing)	About 20GB	300TB is adequate (40 years of use)
Moderate (Gaming/Creative)	About 50–100GB	Above 500TB
Heavy (Server/Lots of Clips)	200GB+	800TB+

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Heat dissipation: hidden dangers of M.2 SSD

The temperature of high-speed NVMe SSD can reach 80–90°C when fully loaded, and the speed will drop significantly after triggering thermal protection.

Solution:

• The motherboard has an M.2 heat dissipation sticker, do not remove it (many people think it is a protective film and throw it away)
• PCIe 4.0/5.0 disks are recommended to be equipped with an aluminum heat dissipation vest or an adapter card with active heat dissipation.
• The air duct inside the chassis is good and the temperature is naturally low

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Capacity planning

Purpose	Recommended capacity
Pure system disk + several commonly used software	256GB (not recommended, fills up quickly)
System + daily software + several games	1TB starting (recommended)
Main creative work computer (video/design)	2TB or more
Dedicated game storage disk	2–4TB

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Shopping list

Core Parameters	Recommendations
Interface protocol	NVMe PCIe 4.0 (mainstream recommendation)
DRAM cache	System disk must have
TBW	1TB capacity recommended ≥ 300TB
Warranty	3–5 years (with TBW coverage)
Cooling	M.2 PCIe 4.0 with vest

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*The technical parameters in this article are derived from storage industry standards and mainstream evaluation methods, and do not represent recommendations for specific brands or models. *