Large Downloads choke speed.

[plupien79]

I've fiddled with my article cache, enable/disable direct unpack, number of connections and now have added a dedicated SSD as my temp drive.

When I download anything bigger than 12G my speed drops from the limit I have set 50MBs I have set down to 25-35.

Background:
Machine is in a VM with 12G of ram and 8 CPU cores.
The HDD the os and completed files are on are not shared with any other VM.
The SSD the temp folder is on is also not shared with any other VM.

pystone over 100k
temp dir 193.8MB
complete dir 89.2MB

I have 400/20 internet courtesy of Spectrum. With the overprovisioning and QoS on the router it runs real world 425/22.

Any tips or help would be greatly appreciated.

[plupien79]

I ran DSTAT and noticed at about the 13G mark that disk activity goes from writing, to equal parts reading and writing.
IOTOP reports that it is indeed sabnzbd that is doing the writing and reading.

This is with direct unpack turned off FYI.

[sander]

If you lower RAM to 6GB, does that threshold go to about 6GB too ... ?

[safihre]

The NZB you are downloading, does it have 1 single file in it or separate RAR files? You can see this by clicking on the folder-icon next to the job name when you hover over the job name.

[plupien79]

YEsterdays file had large files.
Trying right now with a 50G nzb full of 375 meg rars.

Will try adjusting RAM if this show same behavior.

[plupien79]

Ok...
Large NZB containing large files. Ends up doing reads and writes while downloading. - Kills Speed

Large NZB containing small files. Doesn't end up doing reads and writes. - Speed Maintains.

[safihre]

Yes this makes sense, because SABnzbd only writes the file when it has the whole file. When the cache is full it will write the rest to the disk -> slow.
This is a design-flaw that I will fix in SABnzbd 3.x.x version.

[plupien79]

Thanks for the help and the update.