Large / Fast downloads choking my server

[Wardy]

I posted a few weeks ago in the binhex/qbittorrentvpn thread about weird issues when downloading, and high IO wait essentially locking my server up.

Since then, I've done a complete rebuild and have moved over to linuxserver/rutorrent. However, I'm seeing similar issues again.

This is now the 3rd client I've tried, and I can't seem to figure this out.

 

(FYI: My server is 8c/16t with 32gb ram, 1tb sata SSD cache and 5*4TB array (1 parity))

 

Basically, I have a gigabit ISP and everything is hardwired over a gigabit lan. I can download games through steam on my gaming laptop at full speed, regardless of the size of the download. (This laptop has a very fast nvme ssd, so I'm not sure if that makes any difference here). I can also download torrents on the laptop at full speed too - so no traffic management from the ISP.

On the server however, rTorrent will download at full speed for about 5 minutes, then the CPU usage (on rTorrent) shoots to about 20-30%, and the speed will tank down to a steady 25-30MB/s. The CPU usage on unraid seems relatively low, with occasionally 1 thread at 100%, but overall it's sitting at 5-10% usage. 

Previously, using deluge and qbittorrent, a few minutes into the download, the CPU usage would be at around 70-80%, and the entire Unraid UI would become unresponsive. When I looked into it a bit more, the IO wait was 30-50% while this was happening. This time, it seems to be 20-30%.

I've recently swapped the SSD out for a different one, that I know is good, and it hasn't solved the problem.

 

I don't know enough about Unraid and how it deals with writing data to the cache / array to even begin to understand what might be the issue here. Having said that, I can transfer large files across the network to and from the server, and the transfer will happily saturate the line for however long it needs to, and the server doesn't even care. 

 

With that in mind, can anybody tell me if this is hardware or software? 

Or can anyone give me any advice as to how I can start to figure this out once and for all?

 

Any help is greatly appreciated!

[trurl]

Are you sure the torrents are going to cache?

1 hour ago, Wardy said:

download at full speed for about 5 minutes

^This could just be I/O buffering in RAM

 

1 hour ago, Wardy said:

down to a steady 25-30MB/s

And then this^ seems like it could be writing to the array.

[trurl]

Go to Tools - Diagnostics and attach the complete Diagnostics ZIP file to your NEXT post in this thread.

[Wardy]

Just now, trurl said:

Are you sure the torrents are going to cache?

How would I be sure? I can see that they are written to the cache if I go exploring the cache drive from Main.

 

1 hour ago, trurl said:

^This could just be I/O buffering in RAM

I've tried giving rTorrent a lot of ram in the settings, but it never seems to use it in the way I'd expect / at all.

 

1 hour ago, trurl said:

And then this^ seems like it could be writing to the array.

The drives are ~1 year old and parity checks / mover generally run at around 120-180MBs (IIRC).

 

Diags attached.

unraid-diagnostics-20210113-1532.zip

[trurl]

What user share are you downloading into?

[Wardy]

/mnt/user/Storage - cache is set to Yes.

[itimpi]

3 minutes ago, Wardy said:

/mnt/user/Storage - cache is set to Yes.

You are likely to get better speeds if you configure the container to by-pass the User Share level and use /mnt/cache/Storage.  Leave the Storage Share set to Use Cache=Yes (as /mnt/cache/Storage is part of that User Share) if you want files to later be moved to the array when mover runs.