Last Updated: July 2018 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.
To illustrate how fast USB 3.1 is in real-world scenarios, we compared 8 recently released USB mass storage devices in the bar graph below. Results are shown in megabytes per second, based on our sequential non-compressible file transfer tests that involve a single 10GB MP4 and a folder of 5GB JPEGs. Current testbed as of this writing is a late-2014 Apple MacBook Pro Retina running Windows 10.
In this comparison, external SSDs – the Samsung T5 and Western Digital My Passport SSD – are undisputedly the performance leaders. Powered by a decent flash controller, both models ideally would do far better at USB 3.1 Gen 2 (10Gbps). However, for the sake of this comparison, we kept everything at USB 3.1 Gen 1 as all the other drives can’t go any faster than 5Gbps. If you are interested in running applications directly from external drives, these two won’t disappoint.
The next best performers are the Corsair’s Flash Voyager GS and Kingston’s HyperX Savage 3.1. They are both classified as old-fashioned thumb drives in terms of design and intended use-cases. Without USAP, these aren’t designed to run applications as efficiently as the T5 and My Passport SSD but they are more than adequate for moving large files (e.g. media, ISOs) in bulk, in a timely fashion.
For capacity larger than 1TB, nothing beats hard disk drives. 8TB options shown here managed speed at around 180MB/s. By no means are the Seagate Backup Plus and WD My Book slow; traditional hard disk drives are particularly reliable in long-term archival backup as well as incremental backups that likely demand more storage space consumption.
The slowest and the most compact in this comparison is the mini USB drive sub-category. Expect write performance to be on par with that of USB 2.0 storage. Mini drives like Samsung Fit and Sandisk Ultra Fit are targeted at users who need them to stay plugged to a PC or car audio as a semi-permanent storage. Limited by their diminutive size, these drives aren’t exactly built for speed. Yet they are indispensable if you need quick local storage boost for your PC without needing a major upgrade.
This bar chart is by no means an exhaustive comparison of USB drive speeds but it should give you a fairly good idea how each storage type performs in real-world scenarios. We intend to add more drives as needed. Let us know in the comment below what you would like us to add in this comparison.
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