Download speed weirdness

[dannzyx]

Hey All,

Read all the topics about slow downloads speeds, and tried all the tips and tricks to be found in the forums and wiki.
Now the download isn't really slow but there's some weirdness going on with it.

I have an 180mbit internet connection which is stable during all times of the day (yay Netherlands), so I can get about 20/21 MB/s downloads speed at all times.

Here comes the weird part, tested all PC's with the same NZB on the same server in a timespan of a couple of hours over multiple days;

Macbook Pro 2014, i7, 8 GB RAM
Connection: Wifi AC
Download speed 21 MB/s

Connection:Wired 1GB
Download speed: 14 MB/s

Windows 8 PC i5 3570K, 16GB RAM
Connection: Wifi AC
Download speed 21 MB/s

Connection:Wired 1GB
Download speed: 14 MB/s

Windows Server 2011, Pentium G620, 8 GB
Connection:Wired 1GB
Download speed: 14 MB/s

Also measured the data transfer between all PC's via the wired connection, perfectly steady around the 100 MB/s. The data transfer of the Wifi AC is between 30 Mb/s and 50 Mb/s.

So in all Sabnzbd cases, WiFi is faster than wireless while the data transfers between the wired computers is way faster than that of wireless.

Seems like Sabnzbd wired has around an 100Mbit Cap.

My neighbour has the exact same connection as me and the exact same problem; the wired connection is locked at around 14 MB/s.

We tried everything;
- Different cables
- Pc directly to modem
- Different routers (Apple, Asus, TP-Link)
- Different switch

Anyone got any idea?

[shypike]

First, SABnzbd isn't the worlds fastest program.
I'm as surprised as you are at the WiFi speeds.
In fact, it's near the max.
Could it be that the WiFi uses larger IP packages?

[dannzyx]

I'll check of a change in the windows MTU has any effect and report back.
Edit: Quick check on Macbook reveals both ethernet and wifi have the same MTU (1500)

[dannzyx]

Tried nzbget last night and got a steady download of 21 MB/s.
So I guess it's the CPU/RAM that can't handle it (although it doesn't show 100% usage during download).

The strange thing is though, my neighbour has the atom C2750 with 8 cores and also has the 14 MB/s download limit.
Something to do with multicore optimization?

[shypike]

Tried nzbget last night and got a steady download of 21 MB/s.

Is that over the wire or over WiFi?

[nebuto]

Hi,

I'm also experiencing the same issue, i have a 500mbit connection (so 60MB real download speed). I can't remember having a full download speed on sabnzbd, before that i was on a 100mbit connection and i was capping it @ 12MB.

But then i upgraded and never witnessed full speed, at best it's in the 25/30MB range, sometimes it can drop to 2mb, and for noooo reason, cpu process isn't that high.

I thought sab couldn't handle it, so i dled several nzb on both sab & unison (same serv, same nb of connections) and i'm at full 60MB on unison each time, not so on sab.

On sabnzbd :
- I tested fewer connections, no change (I'm on giganews : 50 connections + SSL)
- Reboot, no change
- More cache, no change
- Different usenet server, no change
- Played a bit with some special parameters, regarding CRC errors and random ip address, no change
- I tested on both wire and wifi AC (the wifi speed is capable of handling 60MB),
- Tested on a macbook air and macmini, it's the same, but both macs from the same system backup it might be biased.
- I'm using little snitch, tried completely shutting it off, no change

I'm on a pretty decent macmini : late 2012 / bicore i7 @2.3ghz / 8gig of ram / SSD + HDD for storage (and the hard drive has a writing speed > 60MB obviously) + yosemite.

I wonder if it could be the system, or perhaps the configuration files that is quite old, i think i'm using sab for several years now on the same config, and since it's linked with sickbeard, couchpotatoes and several other service + completion scripts i'm kinda not willing to redo all of that.

If you want more debug info or anything to help i'll be pleased to deliver, i'm also a dev, so if you can point me in the right direction i''ll try debuging this, so far i haven't got any luck :/

[shypike]

The main problem is in the way Python works.
At high speeds it cannot compete with software written in C/C++/ObjectiveC
Probably there's room for improvement, but that's not on the priority list now.