[DRBD-user] confused about using DRBD VBDs with Xen

Jean-Francois Malouin Jean-Francois.Malouin at bic.mni.mcgill.ca
Fri Oct 1 03:31:48 CEST 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


A repost from the xen-users list where I got some hints but nothing
really conclusive.

I can provide more info upon request but for now I'll try to be brief.

Debian/Squeeze running 2.6.32-5-xen-amd64 (2.6.32-21) 
Xen hypervisor 4.0.1~rc6-1, drbd-8.3.8 and ocfs2-tools 1.4.4-3
Both Dom0 and DomU are running 2.6.32-5-xen-amd64.

2 nodes are configured with the following layout:

raid1 --> lv1 -> drbd (r1) -> ocfs2 (mount point /xen_cluster/r1)
      \-> lv2 -> drbd (r2) -> ocfs2 (mount point /xen_cluster/r2)

The r1 drbd resource config (with the obvious changes for r2):

resource r1 {
   device /dev/drbd1;
   disk /dev/xen_vg/xen_lv1;
   meta-disk internal;
   startup {
       degr-wfc-timeout 30;
       wfc-timeout 30;
       become-primary-on both;
   net {
       cram-hmac-alg sha1;
       shared-secret "lucid";
       after-sb-0pri discard-zero-changes;
       after-sb-1pri discard-secondary;
       after-sb-2pri disconnect;
       rr-conflict disconnect;
   disk {
       fencing resource-only;
       on-io-error detach;
   handlers {
       fence-peer "/usr/lib/drbd/crm-fence-peer.sh";
       after-resync-target "/usr/lib/drbd/crm-unfence-peer.sh";
       outdate-peer "/usr/lib/drbd/outdate-peer.sh";
       split-brain "/usr/lib/drbd/notify-split-brain.sh root";
       pri-on-incon-degr "/usr/lib/drbd/notify-pri-on-incon-degr.sh root";
       pri-lost-after-sb "/usr/lib/drbd/notify-pri-lost-after-sb.sh root";
       local-io-error "/usr/lib/drbd/notify-io-error.sh malin";
   syncer {
       rate 24M;
       csums-alg sha1;
       al-extents 727;
   on node1 {
   on node2 {

One domU configured, with file disk and swap image:

root  = '/dev/xvda2 ro'
disk  = [ 'file:/xen_cluster/r1/disk.img,xvda2,w',

/xen_cluster/r{1,2} are OCFS2 filesystems on top of 2 drbd resources,
r1 and r2, primary on both nodes. drbd backing devices are LVs on top
of a md raid1 mirror. With this I can create a DomU and do live
migration between the 2 nodes. good.

I want this to be ultimately running under pacemaker/corosync/openais.
So following the drbd users guide (OCFS2 and Xen sections) I modified
this to:

root  = '/dev/xvda2 ro'
disk  = [ 'drbd:r1,xvda2,w',

Trying to recreate the DomU leads to:

xm create -c xennode-1.cfg
Using config file "/xen_cluster/r1/xennode-1.cfg".
Error: Device 51714 (vbd) could not be connected. Hotplug scripts not working.

Not quite sure what to do now.

Thanks for the inputs.

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