Subject: Re: Large disks and NetBSD 4.0?
To: Jukka Marin <>
From: Ronald Roskens <>
List: netbsd-users
Date: 10/26/2007 18:04:45
On Fri, 2007-10-26 at 14:14 +0300, Jukka Marin wrote:
> Hi,
> I will try setting up a new server with a 3 TB (or so) RAID disk to be used
> for XEN virtual machines.  What is the best way of partitioning the disk -
> is it possible to disklabel disks this big in the normal way or should I be
> using wedges or something?  Do wedges work with XEN?

While I'm still new to setting up Xen under netbsd, here's some things
I've learned:

1- NetBSD as a domU sees the disk you give it as a "real" disk.

While you might assign the domU /dev/raid0e, and further bsdlabel that
partition inside the domU, accessing a particular filesystem under dom0
isnt easy.

Makes it hard if you dont have networking setup between the domU's to
transfer files around, or just want to mount up a domU's filesystems.

2- The standard XEN3_DOM{0,U} kernels do not include the options for
DKWEDGE_* and drvctl.

wedges seem to be pretty cutting edge, and theres not a lot of
documentation written about them. In particular, the ptype argument for
dkctl addwedge isnt well defined. The types arent the same as their
disklabel versions. (ie: ffs = 4.2BSD, lfs = 4.4LFS)

You need to use gpt to create a GPT on the disk, but raidframe devices
do not seem to be supported. If your not using raidframe, then GPT would
seem to give you the flexibility in terms of the number of partitions it
would support as wedges.

The combination of the 2 above have made me decide to do everything
using vnd files.

3- For grub, if your root device isnt automatically detected in the dom0
(say root is on wd2a rather than wd0a), you need to specify rootdev=X
rather than root=X.