Why does download speed plummet when using backup servers?

Get help, report and discuss bugs.
Post Reply
agathorn
Posts: 15
Joined: 08 Jan 2017, 06:15

Why does download speed plummet when using backup servers?

Post by agathorn » 08 Jan 2017, 06:22

Hi there,

I recently switched from SabNZBD to NZBGet because I heard that it has much better performance when running on weaker NAS systems. I have NZBGet running now on my Drobo5N and for the most part I am really impressed. Originaly I had SAB on my main PC and would download around 10 MB/s on my 100Mb connection (I often get above my rated speed). When I moved SAB to my Drobo5N though the speed dropped to about half, or 5MB/s. After doing some reading I found that this was due to the performance limitations and that NZBGet was the answer. So I installed NZBGet onto my Drobo and was immediately impressed to see my speeds jump back to 7-9MB/s which was really impressive so Good Job!

However I am noticing one problem. I get great speeds when the articles have full availability on my primary server, Usenetserver. However when NZBGet falls back to one of my two backup servers (Astraweb and Blocknews) the speed plummets down into the 200-700 KB/s range! :( Pretty much anytime I see "Backup: XX%" in NZBGet, my speed is crap. The thing is though that I don't have this problem in SAB. All three of these servers will be just as fast in that application.

Is there some special handling of backup servers in NZBGet that maybe I need to tweak?

agathorn
Posts: 15
Joined: 08 Jan 2017, 06:15

Re: Why does download speed plummet when using backup server

Post by agathorn » 08 Jan 2017, 07:31

So I did a further test. I noticed one download that was basically constantly falling back to Astraweb and downloading around 700KB/s. Astraweb was a backup server with priority 1. I went into settings and moved Astraweb to priority 0 making it a non-backup server and instantly my DL rate jumped up to 11MB/s. Changed Astraweb back to priority 1, and the rate fell back to 700KB/s.

I think this makes it very clear that there is something odd going on with servers marked as "backup" or higher than priority 0.

kloaknet
Posts: 336
Joined: 23 Jul 2014, 08:52

Re: Why does download speed plummet when using backup server

Post by kloaknet » 08 Jan 2017, 11:24

@hugbug did a little test, and not defining a level 0 server, and only 2 lvl 1 servers (3rd server Active=no, and lvl 0). (ok not the best option, but maybe in time you delete the settings from the level 0 server server as u dont use it anymore). This results in the download not starting at all :D, maybe a warning could be added for the logs, or an automatic switch to the lower levels ;) . (using nzbget 18.0-testing-r1858 service-mode).
Also did a test with a lvl 0 and a lvl 1 server, and then I disabled the lvl 0 server, and then also downloads stops. (the optional option has no impact on this).

@agathorn, note that there is a speed chart, and server enable/disable options right next to the green button: clicking on the truck (upper line) can enable and disable servers on the fly (upto reload of NZBget), and the clock can give you download statistics in a chart (2nd line). This might help to see what is going on using the download stats per server.

hugbug
Developer & Admin
Posts: 7573
Joined: 09 Sep 2008, 11:58
Location: Germany

Re: Why does download speed plummet when using backup server

Post by hugbug » 08 Jan 2017, 11:57

agathorn wrote:So I did a further test. I noticed one download that was basically constantly falling back to Astraweb and downloading around 700KB/s. Astraweb was a backup server with priority 1. I went into settings and moved Astraweb to priority 0 making it a non-backup server and instantly my DL rate jumped up to 11MB/s. Changed Astraweb back to priority 1, and the rate fell back to 700KB/s.

I think this makes it very clear that there is something odd going on with servers marked as "backup" or higher than priority 0.
Higher level servers are used after lower level servers were tried. If the main servers are slow with response that limits the speed and higher level servers don't have enough job to do? By putting astra to main you eliminate the issue. If astra is unlimited then use it as level 0, you can have many servers on the same level. Otherwise increase the number of connections of level 0 servers. If you have multiple level 0 servers make their connection numbers similar because each server is tried before going upper levels. For example if you have two main servers where the first have 10 connections and the second 1 connection then each article which fails on first server will be tried on second too (before increasing level); you can see how having only one connection on second server can limit the speed.


@kloaknet: what you describe is a totally correct behavior. This is to prevent accidential downloading from (costly) block accounts. No active level 0 servers = no downloading.

agathorn
Posts: 15
Joined: 08 Jan 2017, 06:15

Re: Why does download speed plummet when using backup server

Post by agathorn » 08 Jan 2017, 17:51

Astraweb and Blocknews are both block accounts, hence why I have them as backup servers. I can kind of see what you are sayign with it trying the main first and if that is slow, but I have the exact same fallback setup on SAB and it doesn't suffer from the same drop in speed, so I am fairly sure my main server isn't being slow in that regard, unless maybe NZBGet is being a tad slow in determining the status?

Post Reply

Who is online

Users browsing this forum: No registered users and 6 guests