The commonly mentioned transfer speed of a USB flash drive refers to its read and write speeds, which are not fixed values. These speeds are primarily influenced by four key factors: interface type, storage protocol, flash memory chips, and controller chips. Additionally, there exists a difference between “read speed” and “write speed,” with read speeds typically being significantly faster than write speeds.
USB ports are categorized into USB-A (traditional interface) and USB-C (Type-C, referring only to the physical connector shape; compatibility depends on the protocol). The core protocol determines the maximum speed limit. Common types and parameters are as follows:
| Interface / Protocol | Theoretical Transfer Rate | Actual Read Speed | Actual Write Speed |
|---|---|---|---|
| USB 2.0 (Hi-Speed) | 480 Mbps (≈ 60 MB/s) | 10–30 MB/s | 2–10 MB/s |
| USB 3.0 (3.1 Gen 1) | 5 Gbps (≈ 625 MB/s) | 80–200 MB/s | 30–100 MB/s |
| USB 3.1 Gen 2 (10Gbps) | 10 Gbps (≈ 1250 MB/s) | 150–400 MB/s | 80–200 MB/s |
| USB 3.2 Gen 2×2 | 20 Gbps (≈ 2500 MB/s) | 300–800 MB/s | 200–500 MB/s |
| USB4 (compatible with Thunderbolt 3/4) | 40 Gbps (≈ 5000 MB/s) | 500–2000 MB/s | 300–1500 MB/s |
Common Misconception: Type-C Port ≠ High Speed! Many inexpensive Type-C flash drives actually use the USB 2.0 protocol, resulting in slow speeds. Always check the “protocol specification” on the packaging (e.g., USB 3.2 Gen 2).
Flash memory is the “storage core” of USB drives, and its type determines write stability (especially during large file transfers):
The controller chip manages data read/write operations. High-quality controllers (such as Silicon Motion, Phison, and Samsung) maximize the performance of the interface and flash memory, preventing speed “overstating.” Low-cost controllers may exhibit “high theoretical speeds but actual transfer lag.”
Speed parameters on USB flash drive packaging (e.g., “100MB/s”) are mostly read speeds by default, and write speeds are usually only 1/2 to 1/3 of read speeds. Here is a common example:
A “USB 3.0 USB flash drive with read speed 150MB/s and write speed 60MB/s”:
Small files vs. Large files: When transferring a large number of small files (e.g., 1000 photos, numerous documents), the speed is more than 50% slower than transferring a single large file (e.g., a 5GB video). This is because frequent addressing is required, which reduces the “scheduling efficiency” of the controller and interface.
USB drive transfer speeds range from a few MB/s (USB 2.0) to over a thousand MB/s (USB4). For everyday users, “USB 3.0/3.1 Gen 2 flash drives” offer the best value. If handling large files, go straight for “USB 3.2 Gen 2×2 or NVMe protocol flash drives” to avoid efficiency losses due to slow speeds. The key takeaway: Don’t just focus on the physical connector type. Prioritize the protocol and actual write speeds.
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