how does web server allocate data for
multiple hosts..

Its not just a matter of how many people accessing
your sites, there are other sites on the same
drive too. It will depends on how busy the entire server is...
Until you are receiving 100 hits to your site at once,
you are far from having to worry about speed.

FYI, few data centers and web hosting providers offer:

-Linux and Windows based platforms.

I learn this from WMC