22 April 2017, Comments: 79

 Last Updated: April 2017         Ian Chiu

There are currently four speed modes defined by USB 3.1 and USB 2.0 specification. They are SuperSpeed Plus (SSP), SuperSpeed (SS)Hi-Speed (HS) and Full-Speed (FS). The SuperSpeed Plus mode (appended in USB 3.1 specification) has a theoretical transfer rate of 10Gbps. It’s commonly known as USB 3.1 Gen 2 while SuperSpeed or USB 3.1 Gen 1 mode (previously known as USB 3.0) has a bandwidth of 5Gbps.

In comparison, we’ve seen first generation Gen 2 drive (a pair of SATA 6 SSDs in RAID-0) from Sandisk that manages to push the real-world performance close to 900MBps (or 7.2Gbps) whereas latest patch of Gen 1 drives can reach close to 400MBps (or 3.2Gbps). USB 2.0 is still widely used; it delivers both Hi-Speed and Full-Speed mode that operate at 480Mbps and 12Mbps respectively. (Note: the unit is in bits per second.)

When taken account protocol overheads, latency and flow control, the fastest USB 3.1 Gen 1 device should operate at near 450Mbytes per second whereas a USB 3.1 Gen 2 device – in best case scenario – should perform at 1.1Gbytes per second in real-world applications. But your mileage may vary depending on the system. The new Gen 2 mode also reduces overhead from 20% to just 3% with the USB 3.1’s new 128b/132b encoding scheme; hence, you see better effective throughput.

Real-world USB Storage Benchmark

To illustrate how fast USB 3.0 is in real-world scenarios, we plotted a dozen storage devices’ benchmark data in bar graphs so you can easily tell the performance leader in each flash drive subcategory.  Results are shown in megabytes per second, based on our 10GB sequential file transfer tests. Current testbed as of this writing is a late-2014 Apple MacBook Pro Retina running Windows 10.

Tested Corsair Flash Voyager GTX, Samsung T3 and Sandisk Extreme 500 SSD are amongst the fastest USB storage solutions available. These drives are paired with a pretty decent SSD controller as well as enabled with UASP to make the most of USB 3.1 Gen 1.

These benchmark numbers were partially taken from our round-up of high-performance flash drives as well as mini USB drives.  However, Corsair Flash Voyager GS, Kingston HyperX Savage 3.1 and Lexar JumpDrive P20 don’t come with USAP support so expect rather low random read & write speeds.  Having said that, they are best for bulk file transfer (e.g. large media file transfers, ISO backups).

On the other hand, mini drives – namely Lexar JumpDrive S45, Samsung USB 3.0 Fit and Sandisk Ultra Fit – are targeted at users who value drive size over speed.  They are also designed to stay plugged to a tablet, laptop and alike as a secondary storage.  Limited by their diminutive size, these drives aren’t exactly built for speed. Head over to those articles if you want to take a look at the small file performance.

Most Advanced USB Duplicators in the market with feature-rich drive manager software. (AD)

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