can a VM's harddisk be faster than the physical disk?

Alex Muntada alexm at
Mon Jan 10 21:48:12 UTC 2011

+ Stefan Sticht <sticht at>:

> I have a little home-grown box whose VM's harddisk seems
> to be faster than the host's harddisk:

The host buffer cache could be the reason: since most probably
your host has much more memory than the guest, it's possible
that the whole qcow file is mapped on the buffer cache if it's
small enough.

You can try playing with cache values to confirm that, see the
storage section in


Alex Muntada <alexm at>

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