Transfer speed much slower in Wi-Fi than Ethernet

ethernetnasperformancewifi

I'm transferring a lot of pictures from my Macbook Pro to a local Synology NAS (DS116), using an FTP software named Transmit.

I noticed that the upload speed is quite different between Wi-Fi and Ethernet:

  • Using Wi-Fi (ac): ~27 MB/s in FTP mode, and ~22 MB/s in AFP mode

  • Using Ethernet (via a Thunderbolt adapter): ~110 MB/s, in both FTP and AFP modes

I don't understand why the Wi-Fi transfers are so slow compared to Ethernet. Both of them should handle the maximum write speed of the disk (112 MB/s according to Synology).

Any idea about what could be slowing down the transfers when using Wi-Fi?

Notes about my Wi-Fi :

RSSI: -56 dBm

Noise: -95 dBm

TX Rate: 350 Mbps

PHY Mode: 802.11ac

Router: TP-Link AC750

Best Answer

To make it an official answer:

350 Megabit per Second (Mbps) = 43.75 Megabyte per Second (MB/s). Ethernet is always faster and more reliable then Wi-Fi. So when Ethernet is available, use it.

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