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Re: recommendations for a Xen/NetBSD box?



Carl Brewer <carl%bl.echidna.id.au@localhost> writes:

> Thanks Steve, I grabbed that from the Xen user guide just after
> replying.  As the box only has 4GB and I'm planning on giving 2GB to
> the main NetBSD 4.0 instance, and the CentOS instance only needs maybe
> 1GB or so, I don't think I need it?  Do the DomU's need to know about
> it if the Dom0 is managing memory for them?

With 4 GB, if you run i386 (without PAE) on the dom0, then really the
machine will only have 3.25-3.5 GB available due to address space being
taken up for various things.  If you want to parcel out the 3.25 as 2G
to the dom0 and 0.5-bit each to 3 domUs, that will work fine.

I have a xen box running NetBSD 4.0-stable on i386, with 4G physical
ram.  xm info (xen2) reports:

memory                 : 3583
free_memory            : 861

dom0 has 256, and I have 9 domUs with 256M and 1 with 128M.  most domU
are netbsd 4 but some are netbsd 3.  If you don't run a gui it's amazing
how little memory you need.  I am only running xen2 because I have not
gotten around to updating - this is 2 years old.

The issue is that the domU kernel must match the xen mode.

xen and dom0            domU
i386 nonPAE             i386 nonPAE
i386 PAE*               i386 PAE*

amd64                   amd64
amd64                   i386 PAE*

I believe that the only thing you need current for is i386 PAE, starred
above.  There is no reason you have to run the same version of netbsd on
dom0 and domU.  I think you can run amd64 netbsd-4 on dom0, and either
the same as domU or current i386 PAE.

With a 4 GB box, and a xen/dom0 that's amd64 or i386 PAE, you should be
able to use all 4G.  Or go to 8G total.  But there is no netbsd dom0
i386 PAE support yet.  There's no real reason, though - you can use
amd64 as dom0.

Typically people have the dom0 do nothing but run xen and disks, but you
can use it normally too.

What you want to do about RAID is totally sensible, and gets raid for
domUs without them knowing anything about RAID.  See my message linked
From the xen howto about raid installs:

http://www.netbsd.org/ports/xen/howto.html
http://mail-index.netbsd.org/port-xen/2006/03/01/0010.html

This is still accurate I think.  I use files in /n0/xen in dom0
filesystem as my virtual disks for domUs.

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