Performance: virtual vs. non-virtual machine

Dear all,
For a project I've started to set up an own instance of the OSM infrastructure. For now I've started to use the vagrant-machine, so I haven't installed the OSM-website directly on my machine. Unfortunately the performance in the vagrant-instance is not that good as I've hoped. Of course I know that using a virtual machine is not that good, but I've assumed that it is a little bit faster.
One exmaple:
By browsing using the vagrant host from a blank website to the vagrant-osm-instance, the map view using takes about 27 seconds until the map appears.
Is this only caused by the fact that I am using the vagrant machine? At least by checking the performance monitor it seems, that there is enough system capacities and that the system does not run at 100% load.

System: Intel Q6600: 4x3Ghz, 4GB DDR2, 500GB 7200rpm HD - not the best, but as already said: Only for development.

Would be nice to get some feedback :)