virtualbox.org

Hi,
The host is OS X 10.9.latest , guest is Ubuntu 14.04.latest LTE.
Frequently the guest carries out a data transfer of huge data amounts (several GBs) which
takes hours. Transferring is data from usb external storage's one partition to other partition,
or from one usb external storage to other one.
I get the impression that at some time the host is doing energy saving or something similar
and due to this the data transfer on guest pauses or stops.

Anybody else did same observation?
How to prevent energy saving on os x host while guest is doing some data transfer?

Disable App Nap for VirtualBox. Right Click on its icon > Get Info > check Prevent App Nap.

If you're doing this on a MacBook Pro (or even if you're not), then you may want to also turn off computer sleep and hard disk sleep in the Energy Saver control panel while the transfers are in progress.

I was hoping the OP already did that.

"never assume because when you assume…"