First of I noticed that the speed of the external hard disk was very slow compared to the internal SD-card. It was around 900Kb/sec and the internal SD-card was around 3Mb/sec. This speed whet up to the same as the internal SD-card by removing the sync attribute of the usbmount options (in /etc/usbmount/usbmount.conf line 22). So that problem out of the way we can start testing.
Most people complain that SABnzbd is to cpu intensive and to memory hunger and that you should use NZBGet or NNTPGrab instead as they are less cpu and memory consuming. So lets compare the three. The internet connection that I'am using can download at 5.5Mb/sec on a normal desktop with SABnzbd so lets take that as 'control'
|Average download speed (Mb/sec)||5.5||1.7||2.8||0.6|
During this test a 1.5Gb file was downloaded. The download speed of SABnzbd was all over the place from low points of 1.2Mb/sec to some spikes of 2.5Mb/sec. The download speed of NZBGet was much more stable between 2.7 and 2.9, that is more what you would expect. The final one NNTPGrab was the wist of all download speeds never went over 700Kb/sec very disappointing...
The cpu consumption was very high during the download, and he Raspberry is running on 700Mhz by default, so what would happen if we increased the cpu speed?
We got a bit better results with the Raspberry running at 900Mbz (1000 caused a crash)
|Average download speed (Mb/sec)||5.5||1.9||3.0||0.6|
The download speed of SABnzbd was even more all over the place, with low points of 1.2Mb/sec to high speeds of 3.5Mb/sec. NZBGet was a bit better but still a very stable download speed. And NNTPGrab was still to slow.
Conclusion: SABnzbd could be used if your internet connection isn't that fast, or you don't mind waiting. But the best newsgroup downloader for the Raspberry Pi is NZBGet.
Update: Extra "speed boost": Disable CrcCheck (In Settings -> Download Queue) if you have a stable newsserver. This will increase the download speed with NZBGet to 3.7Mb/sec. A possible downside is that if an article fails to download correctly that the entire download needs to go tough a par2 check/repair, which will cost you more time in the end.
Some tech details:
I tested this on a Raspberry Pi model B with with '2013-09-25-wheezy-raspbian' distribution.
SABnzbdPlus version 0.6.15
NZBGet version 11
NNTPGrab version 0.7