[et-mgmt-tools] Re: Virt-P2V problem

[Richard W.M. Jones]

On Wed, Mar 05, 2008 at 09:28:16AM -0800, Collins, Kevin [Beeline] wrote:
> Will do - I assume the fact that the disks are IDE will allow it to work
> even though they show up as sdX? I assume this is just SCSI emulation,
> like some older devices have used?

There's several things going on here:

(1) SATA (which is really IDE) uses the SCSI infrastructure in the
Linux kernel.  So disks appear as /dev/sdX.

(2) Old kernels used a separate IDE infrastructure (/dev/hdX).  But
I'm pretty sure this is all deprecated now and even old PATA IDE disks
will use the SCSI infrastructure and appear as /dev/sdX.  (See also:
http://linux-ata.org/)

(3) In the virtual machine the situation is complicated:

  (a) If the virtual machine is fully virtualized, we emulate an
      old PATA disk controller, so the virtual disks appear as /dev/hdX.

  (b) If the virtual machine has either Xen paravirt drivers installed
      or is completely paravirtualized, Xen has its own block device
      infrastructure and the disks appear as /dev/xvdX.

Virt-p2v attempts to rewrite /etc/fstab after migration so that drive
names are rewritten correctly.  If it doesn't get this right then you
may need to boot the virtual machine in single user mode and edit
/etc/fstab.  (If you have to do this, let me know some details and the
contents of /etc/fstab.p2vsaved and /etc/fstab because it's a bug).

Situation (3)(a) above is slow.  You can improve things for your
Fedora Core 1 system by installing a Xen kernel from a later version
of Fedora, although this is at the moment entering somewhat uncharted
territory so keep a backup.

(BTW, copying this to et-mgmt-tools at redhat.com because it contains
useful info for others).

Rich.

-- 
Richard Jones, Emerging Technologies, Red Hat  http://et.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://et.redhat.com/~rjones/virt-top