Subject: Re: Xen, VT, and RAID
To: Steven M. Bellovin <>
From: Daniel Carosone <>
List: port-xen
Date: 12/22/2006 07:48:04
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On Thu, Dec 21, 2006 at 02:00:46PM -0500, Steven M. Bellovin wrote:
> I'm putting together a new server that will use RAIDframe for RAID-1 on
> two drives.  I plan to run FreeBSD in an fdisk partition using the VT
> support in Xen 3.  The question is what do I do about RAID and that
> partition? =20
> Once choice is to do nothing, and use the corresponding space on the
> second drive for something else.=20

=2E. such as periodic snapshots of the first filesystem, rather than a
live mirror where you get to destroy both copies of your data at once.

> A second is to use FreeBSD's geom mirror on that part of both
> drives.  I have no idea if that will work.

It should, if you give it the two drives.  With a little care about
geometery, offsets, partition names in fstab, drivers and the like,
that may also allow dual-booting that install, either natively on the
hardware or in a Xen HVM, while maintaining the mirroring.

There's no mirroring, but I have a usb flash stick with a NetBSD
install on it, that I can boot natively, under HVM, or as a domU.  The
major pain is the switch from /dev/wd0 to /dev/xbd0, something that
doesn't affect switching a linux install between domU and HVM since
both see /dev/hda.

> A third choice -- is there a third choice?

Hand the freebsd domU a raid1x partition from dom0, rather than a wd0x
partition.  Other than dual-booting without Xen, is there another
particular reason you want to use an MBR partition?

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