Shared storage

1. Configure the network between the two servers
2. Allow through ports 7788-7799 only
3. Install drbd8-utils
4. Change the startup group in /etc/drbd.d/global_common.conf to read:

startup {
  wfc-timeout 10;
  degr-wfc-timeout: 10;
}

1. Create /etc/drbd.d/r0.res:

resource r0 {
  on cloud1 {
    device    /dev/drbd1;
    disk      /dev/lvm1/cloud;
    address   192.168.1.1:7789;
    meta-disk internal;
  }
  on cloud2 {
    device    /dev/drbd1;
    disk      /dev/lvm1/cloud;
    address   192.168.1.2:7789;
    meta-disk internal;
  }
  net {
    allow-two-primaries;
  }
  startup {
    become-primary-on both;
  }
  syncer {
    rate 20M;
  }
}

1. Run drbdadm create-md r0
2. Add drbd to /etc/modules and modprobe it
3. Run drbdadm up r0
4. On one of the nodes only, run drbdadm -- --overwrite-data-of-peer primary resource
5. After sync, run drbd-primary r0 on both nodes
6. apt-get install clvm cman
7. Create a minimal cluster configuration file /etc/cluster/cluster.conf:

<cluster name="vmachines" config_version="1">
  <cman expected_votes="1" two_node="1">
  </cman>
  <clusternodes>
    <clusternode name="cloud1" votes="1" nodeid="1">
      <fence>
         <method name="1">
           <device name="dummy" nodename="cloud1" />
         </method>
      </fence>
      <unfence>
        <device name="dummy" nodename="cloud1" action="on" />
      </unfence>
    </clusternode>
    <clusternode name="cloud2" votes="1" nodeid="2">
      <fence>
         <method name="2">
           <device name="dummy" nodename="cloud2" />
         </method>
      </fence>
      <unfence>
        <device name="dummy" nodename="cloud2" action="on" />
      </unfence>
     </clusternode> 
  </clusternodes>
  <logging to_syslog="yes" to_logfile="yes" syslog_facility="daemon" syslog_priority="info">
  </logging>
  <fence_daemon post_join_delay="3" />
  <totem rrp_mode="none" secauth="off"/>
  <fencedevices>
    <fencedevice name="dummy" agent="dummyfence" />
  </fencedevices>
</cluster>

1. Create /sbin/dummyfence with the conents:

#!/bin/bash
echo "success: dummyfence $2"
exit 0

1. chmod u+x this
2. Create /var/run/lvm directory
3. Run /etc/init.d/cman and /etc/init.d/clvm
4. pvcreate /dev/drbd1
5. vgcreate --clustered y lvm_r0 /dev/drbd1

Enabling CLVM is as easy as setting locking_type=3 in lvm.conf. Possibly run lvmconf --enable-cluster on live systems.