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Re: Xen kernel & tools recommendations

Erik Fair <fair%netbsd.org@localhost> writes:

> If one were setting up a system with Xen to virtualize multiple NetBSD
> guest instances and no other OS, what version of the Xen hypervisor
> kernel, and which xen management tools are best, where “best” is:

A somewhat tough question.

I will assume you are talking netbsd-6 for the dom0.  netbsd-7 is almost
certainly ok, too, but I tend to be conservative abotu dom0 code.

I recommend amd64 for the dom0, partially due to xentools42 building
issues (below) and partly because I think that's the normal path these

Note that modern xen is all PAE for i386.  So you can use the
i386 XEN3PAE_DOMU kernel, or amd64.

PCI passthrough is a recurring problem.  If you don't need it, don't

In the howto, note that boot.cnf lets you boot xen with our bootloader,
and you don't need to deal with grub.  man boot.cfg has an example.

> They work.
> They’re being actively worked on for bugs/improvements, not abandon ware.

The versions in pkgsrc seem to be a bit behind what the upstream xen
project is using.  However, 4.1 and 4.2 are getting security bugfixes
(via backporting, sometimes).

xen 3.1 and 3.3 are really only of historical interest at this point, or
for people that are still running them and haven't upgraded.

Given all that, I would say that you should choose from


and then install the matching xentools.  On 4.1, I am using "xm", but
that is deprecated and "xl" is recommended; it may be the only way on 4.2.

I have found that xenkernel42 does not build on netbsd-6 i386 due to
compiler issues with the included qemu.  (It needs qemu to support HVM

For a new install, I would recommend 4.2.

> They perform well (i.e. the hypervisor and associated toolset impose minimum overhead on the guest OSes).

That's not really been a big issue; overheads are reasonable and not
particularly different from ersion to version.   If you care about
overhead, I'd recommend running PV guests.

The biggest performance issue will be how you provide storage on the
dom0 to hand to domU via xdb.  I tend to have files in the dom0, which
has some overhead vs raw disk (< 10% usually), and then there is some
speed loss from e.g domU rxbd0e to the dom0 file, again < 10%.

Your other likely big issue will be having enough memory so that each
domU has enough not to page and you don't run out.  But if you stay away
From that problem, it should work well.

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