[vbox-dev] VirtualBox faster than actual hardware?

Joseph Miller josephcmiller2 at gmail.com
Wed Dec 9 13:05:34 GMT 2009

I am new to this list and I am not sure if this idea has been addressed in
the past, so please forgive me if it has.

Most virtualizers end up with performance somewhere in the range of 98% to
99% of running on real hardware (AFAIK).  This is pretty good considering
what they have to go through in order to run guest systems.  But it is well
known that the perfomance bottleneck in most desktop systems is in the disk
access area.  I think this is an area where VirtualBox could actually exceed
the performance of actual hardware.

Operating systems disk access are limited by several factors like the type
of filesystem that is being used and the number of files (not just the size)
that must be loaded at any given time.  However, it is common that groups of
files are all loaded in a certain sequence or basically *at the same time*
such as when the OS is booting or when a particular program is loading and
all its data files and libraries must be loaded.  Since disk access is
virtual with VirtualBox, the mapping of these disk sectors on the virtual HD
vs the physical HD doesn't have to be the same.  Perhaps it would be
worthwhile for VirtualBox to keep an index of which sectors are commonly
loaded together and to either physically group these together on the
physical HD (with mapping to their virtual location of course) or a simple
disk caching mechanism.  For files that are changed constantly (data files)
the former may be a better solution but may carry difficult technical
hurdles.  The latter would be fine for most static data (such as libraries
or OS booting files).  If this data can be loaded sequentially (if the host
has a sufficiently non-fragmenting filesystem) performance can be
*significantly* improved.  Maybe I could finally get that reiserfs
performance on my XP guest :)

Please let me know what you think.  I do not think that I have the technical
ability to implement this on my own, I'm mostly a PHP hacker, but I would
contribute in any way I can if this is reasonable.

Thanks for your consideration.


(P.S. - I just *inherited* a dual-head display and am wondering if there is
any development on using a physical graphics card directly in the guest
system. I googled but couldn't find anything.)
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