Re: linux dom0 versus NetBSD dom0

[Roger Pau Monné <roger.pau%entel.upc.edu@localhost>]

2012/1/11 Brian Buhrow <buhrow%lothlorien.nfbcal.org@localhost>:
>        Hello.  I realize the subject of this message could be viewed  as
> inflamatory, but I hope people won't take it that way.
>
>        As part of my day job, we're looking at implementing a large Xen
> installation.  We are a long time NetBSD shop, but for this project, we're
> trying to evaluate the pros and cons of selecting Linux versus NetBSD as
> the platform on which to build the core of our infrastructure.  As part of
> that process, I have the following questions for this group:
>
> 1.  Does anyone have i/o bench marks comparing network and disk throughput
> when using Linux versus NetBSD as Dom0?

There's an old disk benchmark that compares Linux vs NetBSD Dom0
performance, it's really old, so I don't know how much of this is
still true:

http://lsi.vc.ehu.es/pablogn/docencia/configuraciones/xendom0/xendom0.html

> 2.  We know we can use the xbd driver
> to provide virtual disks in NetBSD, but are other storage technologies
> mature in the NetBSD environment?  I'm thinking aboutthings like ISCSI,
> NFS, or other network storage technologies.

Storing DomU images in a NFS is a no go for NetBSD, trying to boot a
DomU that has it's disk on a NFS will make the NetBSD Dom0 kernel
crash. Here is the related PR:

http://gnats.netbsd.org/40726

With no solution (I've tried this with a September build of -current,
and the problem is still there, I don't know if this has been fixed in
the meantime). You can however use iSCSI, as reported by Stephen
Borrill:

http://mail-index.netbsd.org/port-xen/2011/10/31/msg007039.html

Starting and stopping machines can make -current kernel crash (from
September), will try to submit the relevant PR tomorrow if it also
happens with present version of -current, because I've completely
forgot about this.

Also the only image format available on NetBSD is raw or physical
partition (LVM included), qcow, qcow2 or vhd are only available on
Linux right now, due to the fact that NetBSD has no grant table device
that allows access to grant references from userspace programs (and
also has no blktap support).

> 3.  How far behind is NetBSD in the general Xen  development cycle?  In
> looking at the http://www.xen.org web page, it looks like Xen-4.x is the
> current release of Xen.  Will this be the  Xen release built into NetBSD-6?
> Are there particular features that work or don't workin NetBSD versus
> Linux?

Apart from the ones exposed above, libxenlight toolstack (xl), which
is supposed to replace xm is still not working on NetBSD. This should
be fixed soon (as we are working pretty hard on getting this done the
right way), I hope that next major Xen version (4.2) will have full
NetBSD support out of the box :)