Vista - Virtual machine VHD file on USB2

I have been storing my VHD and VMC files on USB2 connected hard drives
(2.5" such as WD Passport). According to discussions here this should
actually speed up performance and it makes the guests portable too.

But now I have stumbled across an issue that maybe someone here has
investigated:
Is there a speed penalty if the USB disk is attached not directly to
my WinXP computer USB connector but instead to a powered USB2 hub
attached to one of the USB2 posrt on the PC?
I have too many gadgets now and I want to clan up my desk by using a
7-way (D-Link) USB2 hub to handle all of my guests (only one running
at a time though).

I realized that this introduces one extra layer of USB and maybe this
will slow down the guest?

Anyone with info on this?

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Bo Berglund (Sweden)