SABnzbd Forums

Hi,

I have this (may be not so) weird problem:

When I download stuff, my download speed is much lower than with other clients. But when I set a cache of 120M then the download speed is good for as long as the buffer is not full. When the buffer is full (119MB) then the download speed drops from 5,5MB/s to 1,5-2,5MB/s. I run on Windows Server 2k8 Standard Edition and the server has 4Gigs of RAM with an average load of 30%.

How is this possible and how can i fix this?

Greetings,
Naxiuz

(Btw.: besides the download speed, sabnbzd really is a great program)

It looks like you have very slow disks.
Maybe you set your cache bigger.
The idea is that SABnzbd can keep a full file in memory.
So if the average content of your NZBs consists of 100 MB RAR-segment files,
you'd need about 140M of cache.
You may also set it to -1, then it will use as much memory as needed,
which is about 130% of the largest file.
If that doesn't help either then somehow writing to disk takes a long time.

BTW: if your download speed is high enough you'll eventually reach the point where
the yEnc decoder cannot keep up with the downloading process.
It will start pausing the downloader periodically.
Given your average CPU load, that should not be the case.

Thanks for the elaborate answer! Things are more clear to me now.

The only weird thing is that the size of the buffer doesn't matter. Setting the cache to 50M will eventually lead to the same download speed as a buffer of 500M for example. The only difference is that it takes longer for the buffer to fill up and therefor my download speeds are high for a longer time. I have to admit I haven't tried to set the cache to -1. Ill try that now.

But can my raid5 array of 3 brand new 750GB disks be really that slow that it cant even keep up with my download speed? When I copy a large file the disks run a lot faster (to approx 20-25MB/s).

Maybe it's the specific pattern?
When the memory cache is full, individual articles are dumped to disk.
So, that's lots of relatively small files.
When assembling the completed files, all articles on disk are read
again to be written to the final file.
Therefore with a memory cache that is too small, each article
is written twice and read once.

Well I found the solution... it has indeed nothing to do with Sab. My Raid5 array was terribly slow even the downloads couldn't keep up with it.

Thanks again!