16 June 2012

USB speed, physical vs virtual (VirtualBox)

Pen drive directly attached to the host.
While the DVB-T RTL USB stick is travelling towards my shack, I am trying to understand if I can install all the software in a virtual machine instead of my powerful host system.

Main concern: would the VirtualBox USB emulation be fast enough for the raw bandwidth required by the RTL stick?

I did some tests using a new USB pendrive. On the host system the benchmark suite peaked reading at 14.8 MByte/s. This is probably enough for the RTLSDR application.

Same pendrive, benchmarked in the virtual machine.
Next I moved the USB stick to the VirtualBox guest using the standard settings. Sequential reading reduced to 7 MByte/s, and all other values were scaled down.

Pendrive in the guest with USB2 enabled.
With a bit of googling I discovered that VirtualBox (4.1.16) has an extension pack that provides emulation of USB 2.0 EHCI. Downloaded, installed, rebooted: results were disappointing! Speed reduced even further, therefore the new driver probably only adds a hardware compatibility layer and not additional speed..

Nevermind. 7 MBps could be enough for running the RTL-based SDR in a virtual machine. If not, I will take the risk of installing everything on the host and enjoy VHF/UHF scanning.