very slow network performance with sabnzbd downloading

[dcrenshaw]

Scenerio:
Dell M4500, 320GB SSD, 8 Core x 3.0Ghz, 8GB RAM, running Xubuntu 12.10 _64bit, NetNAS NV+ as backend media storage for XBMC; mouted using 'cifs', router is the Motorola SBG6580 cable modem with 30/10 Mb/s service. PC Connected wireless at 144Mb/s., NAS connected wired to the router at Gigbit.

1. Copying files from the SAB 'local attached' dl directory 'after manually post processing' to the NetNAS while the next file in queue is dling.
2. cp process transfers across network at the very slow speed of 50KB/s.

Only the network IO appears to be affected, all local activity, Desktop performance, cp, mkdir, mv etc for local drives actions not impacted.

workaround: If I pause the SAB queues while I'm copying the files to the NAS, the transfer rate increases to 4MB/s. What I'd expect to see with the wired, cifs connected NAS on a 144Mb/s wireless connected PC.

What I cant figure out is where the bottleneck is causing this (while copying file).
top reports avg load across the 8 cores as: .23 .26 .31
with the top 4 or 5 running applications consuming CPU % as:
SAB = 14%
cp = 10%
thunderbird = 6%
firefox = 6%

Memory utilization is 6GB of the 8GB available, no swap is being used.

iotop traffic basically does not exist:
occasional spikes when SAB dl's are being written to local disk of around 80 - 150KB/s
cp process at 50KB/s

Wireshark analyzer monitoring packets in and out of the interface report wireless network utilization just under 10% or 1.5MB/s. If I pause SAB it hits 50% utilization while copying files to the NAS.

There appears to be nothing on the system that can be easily pointed at. Any ideas?

[shypike]

So you both download from Usenet and write to the NAS over your wireless connection?
In that case download and copying will compete for the scarce wireless bandwidth.

[dcrenshaw]

I get what your saying but the total network utilization to/from the the UNIX box is not even peaking 10% of capacity possible while SAB is downloading. That's what don't make sense. Pause SAB and I can get the network utilization up to 80% when moving lots of data around. The most stressful head ache is when trying to use a GUI file manager like Commander; when you select a network resource while SAB is downloading it takes 15-20 minutes for Commander to return a dir listing. From the command line it is faster but still takes 5 minutes or so.

[jcfp]

Welcome to the wonders of wlan. Also keep in mind that downloading from usenet involves many simultaneous connections with the server at the same time. That may not go down well with the wireless or even the router, compared to a file copy over the lan that typically uses just a single connection. Try setting the number of usenet server connections as low as possible.

[dcrenshaw]

Well more troubleshooting and I've found that Wired = no issues; I've started recompiling some new WLAN drivers to see if that solves the Wireless issue. The stock generic driver used by XBuntu has no configurable options; downloaded the intel driver source for the nic and see what comes of that.

[dcrenshaw]

SOLVED:
updated wlan driver for Intel and is working good.
SAB dling at 3.4MB/s
sysload at: 3.40, 3.21, 3.00 << huge improvement!
Copying files to NAS at 4MB/s
PC wlan0 utilization on 144Mb/s wireless connection = 41% << as expected with the NAS overhead bottleneck
Also iotop utilization is more on par as expected, seeing the drives read/write speeds steady without the spikes.