gregeric wrote: ↑
Wed Mar 14, 2018 2:28 pm
Don't overlook that the onboard enhanced 5MHz WiFi, on a bus orthogonal to USB, will give you ~100Mbps concurrent with USB disk access.
Nope. At least not when you talk about the numbers presented in the announcement blog post: https://www.raspberrypi.org/blog/raspbe ... le-now-35/
The numbers shown there are the '1m away from AP with nothing in between' throughput. Those conditions where you can use always also a really short Ethernet cable. Once we switch to real-world scenarios performance drops a lot.
When I did some tests last year with my RPi 3 it looked like this:
* RPi 3 being 50cm away from AP: 37.4 Mbits/s on average and over 3000 retransmits when testing in RX direction.
* 4 meters away, 2 walls in between, wall angle approx. 30°: 20.2 Mbits/s on average, a lot of retransmits and already ICMP packet losses.
* 5 meters away, 2 walls in between, different direction compared to prior location: 12 Mbits/s on average, a lot of retransmits and working remotely over SSH felt pretty sluggish.
That was 2.4GHz band which is close to unusable in my area in the evening hours and on the weekends since overcrowded (I spotted ~150 wireless networks back then, only 10% using 5 GHz). So with B+ while being able to escape the overcrowded 2.4GHz band the situation with 5GHz might look better due to less congestion (neighbours 'polluting the air') but of course the same performance drops occur once there is some distance between board and AP and stuff in between. Also the longer waves in 2.4GHz band are better suited to longer ranges and transmission through walls and solid objects.
And unfortunately we get on the new board not even 2x2 MIMO but only a single antenna solution. In my tests MIMO was always key to performance (and also reliability with larger distances).
So no, I'm really not thinking about accessing disk storage through Wi-Fi since it will be a lot slower and less reliable than Fast Ethernet with all the older RPi.
And I've to admit that I'm a bit surprised that nobody seems to have done some serious testing already. Those iperf numbers shown are more or less irrelevant. Wireless numbers since using 'ideal conditions', Gigabit Ethernet numbers not taking 'shared bus' into account.
Edit: just to be clear: I do not
complain about Wi-Fi situation with RPi 3 B+ since dual band capability is highly appreciated to escape overcrowded 2.4GHz band. It's just that those '100 Mbits/sec' do not reflect reality (Wi-Fi is shared medium and 'environment' matters more than anything) and that this onboard Wi-Fi is both too slow and too unreliable. I know how I can get sufficient Wi-Fi with any SBC but those RTL8812AU or RTL8814AU USB dongles with 2 or even 4 antennas have both high power demands and are pretty expensive.