Cubox USB bus limits?

Starting to see some USB bus contention / limits being hit on cubox (ref: http://www.solid-run.com/phpbb/viewtopic.php?f=9&t=635)


I have 2 usb sounds card(s) and 1x usb HDD (will move to eSATA when I get a new housing) running off an unpowered hub on USB bus 2 .. i.e.


root@cubox:~# lsusb
Bus 002 Device 020: ID 0d8c:000c C-Media Electronics, Inc. Audio Adapter
Bus 002 Device 019: ID 0bc2:3300 Seagate RSS LLC 
Bus 002 Device 018: ID 145f:0090 Trust 
Bus 002 Device 017: ID 05e3:0606 Genesys Logic, Inc. USB 2.0 Hub / D-Link DUB-H4 USB 2.0 Hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The USB HDD is powered .. I've seen other posts recommending using a powered hub and ensuring devices are shared over the 2 ports .. any limits here. I was hoping to run a second USB HDD to pair the existing for back-up. Over-night I found mpd had stopped (possibly during maintenance - still investigating). During 'working' operation MPD is, on occasion, reporting ..



Jun 17 09:20 : output: "Lounge Speakers" [oss] failed to play: Write error on /dev/dsp2: Broken pipe
Jun 17 09:20 : output: "Lounge Speakers" [oss] failed to play: Write error on /dev/dsp2: Broken pipe

I'm also seeing the following in syslog

Jun 17 09:20:34 cubox kernel: [829633.363960] orion-ehci orion-ehci.1: sitd_submit: can't schedule iso stream
Jun 17 09:20:34 cubox kernel: [829633.373964] cannot submit datapipe for urb 0, error -28: not enough bandwidth
Jun 17 09:20:34 cubox kernel: [829633.390285] orion-ehci orion-ehci.1: sitd_submit: can't schedule iso stream
Jun 17 09:20:34 cubox kernel: [829633.397412] cannot submit datapipe for urb 0, error -28: not enough bandwidth