Why Can a 1Gbps Network Never Transfer Files at 1GB/s?

[Unison]

Something that can be confusing with network speeds is the difference between bits and bytes.​

A standard Gigabit Ethernet connection is rated at 1Gbps (1 gigabit per second).

There are 8 bits in a byte, so:

1,000Mbps ÷ 8 = 125MB/s

That means even under perfect conditions, a 1Gbps network has a theoretical maximum of about 125MB/s, not 1GB/s.

In the real world you'll normally get less than that because some of the bandwidth is used by Ethernet, TCP/IP and other protocol overheads. The speed of the drives at either end can also become a limitation, especially when transferring lots of small files.

So seeing something around 100–115MB/s when copying a large file over Gigabit Ethernet can actually mean the network is performing pretty well.

It's an easy mistake to make because Mbps and MB/s look very similar, but that capital B makes quite a difference.

What sort of transfer speeds do you get across your home network, and have you ever upgraded to 2.5GbE or faster?

 

[Janobi]

To get anything even close to these speeds you're going to need some decent equipment. General ISP router isn't going to allow transfer of data at that kinda speed. And even then, the 1Gbps is theoretical, as there is an overhead in the frames, and you'll never use 100% of the bandwidth, as keepalives, BPDUs and various other stuff still needs to be sent.

I've used 1Gbps/10Gbps/40Gbps networks but that's enterprise level stuff, with data centre hardware, and fibre optic cabling, fibre switches and SANs.