Speeds capped about 1MB/s when running on a VM

[cornucrapia]

Lately I haven't been able to seem to get downloads much above 1MB/s, at least on instances running on a VM.
I can't say with perfect certainty, but I'm pretty sure this wasn't always the case. I moved from bare metal to a VM relatively recently and I don't recall seeing a performance drop like this when I first set it up or I would have investigated more then. Details about my setup:

* Sabnzbd 4.2.3 running in a container from linuxserver
* Host OS is Arch Linux, recently updated
* Hypervisor is XCP-NG 8.3
* i5 8500t, 4 cores and 16GB RAM allocated to the VM

Wrench results:

Used cache
4.1 MB (6 articles)
System load
0.21 | 0.21 | 0.27 | V=153M R=102M
System performance (Pystone)
389271 Intel(R) Core(TM) i5-8500T CPU @ 2.10GHz AVX2
Download folder speed
102.9 MB/s /incomplete-downloads
Complete folder speed
102.8 MB/s /downloads
Internet Bandwidth
31.4 MB/s 251.2 Mbps

It's not my ISP or router (I don't think) because if I spin up sabnzbd in a container on docker desktop on my workstation I can pull about the 30MB/s that I would expect from my connection.

It doesn't seem to be the disk since a) the wrench reports much faster folder speed than I can download and b) if I spin up another instance of the container without the mounts I get the same speeds.

I have another VM running basically the same stack on another host, and it can get about 12MB/s under the same (as far as I can tell) conditions. Which is definitely a lot better but still about half what I'd expect. If I could get the other one up to 12 I'd be pretty happy but I have no idea what to change to get it there.

Neither VM has dynamic memory, it's fully allocated in each case.

I tried rolling back to an earlier version of Sabnzbd with no luck. I've also tried nzbget and had the same results, so I recognize this isn't directly an sabznbd issue, but it's also so specific to this use case that I'm not sure where else to turn for troubleshooting ideas.

The speed cap is consistent whether it's one of the test nzbs from the wrench icon or a more traditional release. Any ideas what I should check next?

[jcfp]

The speed cap is consistent whether it's one of the test nzbs from the wrench icon or a more traditional release. Any ideas what I should check next?

The speeds you mentioned closely align with 10 resp. 100 Mbit/s ethernet limits, suggesting the VM's network is capped at that for some reason even if your actual connection is more capable.

[cornucrapia]

The speeds you mentioned closely align with 10 resp. 100 Mbit/s ethernet limits, suggesting the VM's network is capped at that for some reason even if your actual connection is more capable.

I'm not sure I understand. From my speed tests within sabnzbd I'm able to connect to my download folder (mounted as an SMB share and accessed over the network from my NAS, which is a separate physical device so definitely no in hypervisor networking) at 1gbps speed, and the speedtest for internet connectivity from sabnzbd is about 300mpbs, which is the speed my ISP offers. The bottleneck is specifically for downloading from usenet. How can my VM's network be capped if I'm able to obtain those speeds on it for other tasks?

[sander]

After a download, in the Wrench, is there anything about "download speed limited by"?

How many connections have you have defined per newsserver?

Have you set a download bandwidth limit?

Have you tried with the reference test download via the Wrench?

Where on earth are you?

[cornucrapia]

- No "download speed limited by"
- I've tried anywhere from 1-50 with no observable change in performance
- Do you mean in the tuning section under general? I have tried configuring that to my line speed (30MB) and allocating 90-100% to it with no observable change, I've also run it with those fields blank
- Yes, same speed is observed with any of the reference test downloads regardless of size
- Western Canada

[sander]

What happens when you create a new VM with a fresh SABnzbd setup?

Do not touch bandwidth settings.

[cornucrapia]

I've tried it on another VM. I can pull slightly higher speeds (10MB/s). Weirdly as I was typing this I noticed I hit 33MB/s for about a minute on my original setup before tapering back down to 2.6MB/S currently. I'm super confused here.