The WD My Passport SSD 2020 sets new speed records for portable SSD. It has a couple of speed tricks under the bonnet but to get the most out of it; you need a PC with a USB-C 3.2 Gen 2 or Thunderbolt 3 port.
First trick – the WD My Passport SSD 2020 is a version of the WD Blue SN550 NVMe – a great midrange SSD. When connected to an M.2 PCIe port, it achieves speeds of 2365.6/1913.5Mbps (Seq. R/W). It does not have a fast DRAM Cache (like WD Black), so it uses some emulated SLC cache to maintain speeds at least commensurate with the USB-C 3.2 Gen 2 interface. Most external USB connected devices don’t have a bucket of cache.
Second trick – The transfer protocol UASP (Universal Attached SCSI Protocol) is now called NVM Express – that denotes some SCSI-like intelligence. With the right PC, it offers up to 70% faster read and 30% faster write speeds over USB 3.
A note on interface speeds
Unless you have a computer that supports USB-C 3.2 Gen 2 (up to 10Gbps data transfer – almost full-duplex) or Thunderbolt 3 (up to 40Gbps full-duplex) then the only speed you will get from an external SSD is what your interface allows.
1.0 – up to 12Mbps (HD) – black keyed port and cable up to 5 metres
2.0 – 480Mbps (HD tops out at 280Mbps) – ditto
3.0 – 5Gbps (HD tops out at 3.2Gbps) – blue keyed port and cable to 3 metres
3.1 Gen 1, similar to 3.0 but FD using a dedicated .8m rated cable
3.2 Gen 2 – 10Gbps FD using a dedicated .3m rated cable
Thunderbolt 3 – up to 40Gbps FD using a dedicated .3m cable
Note 1Mbps = .125MBps = .001Gbps or .000125GBps.
Finally sustained data transfer speeds depends on three things:
The number, type and size of files.
If they are contiguous (all together) or fragmented over the host drive.
If the external drive has any DRAM cache (most do not due to power interruption issues) or emulates SLC (single-level-cell like SRAM) from its TLC or QLC VNAND memory. More expensive external SSD do this and handle larger files better.
We tested on a Microsoft Surface Pro with its USB-C 3.2 Gen 2 (10Gbps=1250MBps) and an HP x360 Spectre 2019 Thunderbolt 3 – this drive flies!
While all maker quote Sequential read/write of MBps speeds this means copy large amounts of contiguous of data from (read or restore) or copy data too (write ore backup) the drive.
The real-life test is random read and write of both small and large drives. Why? Because this is where you see the limitations of the USB connection and the drives ability to cache lots of small or large files to smooth out data transfer. This is pretty good!