Data speeds – USB2, FireWire, USB3, eSATA, PCIe

I’ve been asked recently about the fastest connection speeds for external hard drives and what the quickest options are.  My notes so far:

Mb = Megabit,
MB = Megabyte,
Gb = Gigabit,
GB = Gigabyte.
8Mb = 1MB, 8Gb = 1GB.

  • FireWire 400 – 400Mbps
  • USB 2.0 – 480Mbps
  • FireWire 800 – 800Mbps
  • eSATA – 3Gbps
  • USB 3.0 – upto 5Gbps
  • Thunderbolt – 10Gbps


So Firewire 800 should be quicker than USB 2, but USB 3 is quicker still – and the latter is the most commonly available option.

If you don’t have USB3 and are looking at adding e.g. a PCIe to USB card, then check the motherboard specs.  PCIe speeds are dependent on whether it is PCIe 1.1, 2.0 or 3.0 and whether it’s PCIe x4, x16 etc

e.g. PCIe 3.0 x4 connection (3.94GB/s) should have nearly the same bandwidth as PCIe 1.1 x16, or PCIe 2.0 x8 (both 4GB/s)


So the full speed of the USB 3 probably isn’t achievable over PCIe, but is probably still the best / quickest option when connecting most external hard drives.

If I’ve got the wrong end of the stick on any of this, I’m sure somebody will let me know!