Re: [Xen-users] Re: using DRBD VBDs with Xen

[Vidar Salberg Normann <vidarno@xxxxxxxxx>]

On Thu, Sep 30, 2010 at 11:48 PM, Jean-Francois Malouin
<Jean-Francois.Malouin@xxxxxxxxxxxxxxxxx> wrote:
> * khris4 <khris4@xxxxxxxxx> [20100930 17:19]:
>>
>> okay, now my memory is coming back on setting up DRBD. The reason it's not
>> working is because your tell xen to start the domu with drbd script. If you
>> look at the block-drbd script in the /etc/xen/script/ directory to wil see
>> the drbd only handles making the drbd resource primary and then hands off
>> the device listed under disk in your drbd config to the domu to boot the
>> operation system.  Let give you an example,
>>
>> Here is my setup at my office.
>>
>> hardware raid10 --> lvm -> drbd -> domu   <- what this mean is my server has
>> raid into setup in lvm, then I create lv's for each
>> drbd virtual disk I wanted to create.  so /dev/XEN00/proxy --> is setup as a
>> disk in drbd.conf as resource proxy. Now when you look in my domU proxy
>> config you will see this  disk = [ 'drbd:proxy,xvda,w' ]. This works because
>> each virtual drbd resource has a lv parition with an operating system behind
>> it.
>>
>> The reason your setup is not working is because you handing the domu an drbd
>> virtual device that has file-system behind it and when you domu boot up xen
>> doesn't know it need to mount the drbd and then give a file back-end. You
>> going to need to write a script to handle some of this work or ask if anyone
>> had a script already made.
>
> hmmm, now I'm really confused.
>
> This is what I'm doing on one node:
>
> raid1 ----> lv -> drbd (r1) -> ocfs2 (mount point /xen_cluster/r1)
>       \->  lv -> drbd (r2) -> ocfs2 (mount point /xen_cluster/r2)
>
> so the VBD should look like
>
> disk = [ 'file:/xen_cluster/r1/xennode-1/disk.img,xvda2,w',
>         'file:/xen_cluster/r2/xennode-1/swap.img,xvda1,w', ]
>
> as I've read in the drbd user guide on how to integrate drbd, ocfs2
> and Xen. If I use that VBD file: type in the DomU config I can perform
> live migration.
>
> I don't understand what you're telling me here!
> what is /dev/XEN00/proxy?
>
> sorry for being dense,
> jf

I experienced the same problem and discovered this link:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=588406

It seems there is an error in /etc/xen/scripts/block for Xen packaged for
Debian Squeeze, perform the changes mentioned in that link and I
believe you will be able to use your drbd resource as a disk - it worked for me.

Regards,
Vidar

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