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Date: Mon, 17 Mar 2008 14:09:13 -0700
From: Julian Elischer <julian@elischer.org>
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To: Matthew Dillon <dillon@apollo.backplane.com>
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Cc: Alexander Sack <pisymbol@gmail.com>, jgordeev@dir.bg,
	"Andrey V. Elsukov" <bu7cher@yandex.ru>,
	Robert Watson <rwatson@freebsd.org>, freebsd-hackers@freebsd.org
Subject: Re: vkernel & GSoC, some questions
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Matthew Dillon wrote:

>     In all three cases the emulated hardware -- disk and network basically,
>     devolves down into calling read() or write() or the real-kernel
>     equivalent.  A hypervisor has the most work to do since it is trying to
>     emulate a hardware interface (adding another layer).  XEN has less work
>     to do as it is really not trying to emulate hardware.  A vkernel has
>     even less work to do because it is running as a userland program and can
>     simply make the appropriate system call to implement the back-end.

And jails and similar have the absolute minimum..
at the cost of making a single accessible point of failure
(the one kernel).