Red Hat cluster: Failure of one of two services sharing the same virtual IP tears down IP (RHEL 5.5)

I'm creating a 2+1 failover cluster under Red Hat 5.5 with 4 services of which 2 have to run on the same node, sharing the same virtual IP address. One of the services on each node (called disk1 and disk2 in cluster.conf below) needs a (SAN) disk, the other doesn't (they are called nodisk1 and nodisk2). So on each node there should be one service needing a disk (diskN) and its corresponding service which doesn't need a disk (nodiskN). I'm using HA-LVM.

When I shut down (via ifdown) the two interfaces connected to the SAN to simulate SAN failure, the service needing the disk is disabled, the other keeps running, as expected. Surprisingly (and unfortunately), the virtual IP address shared by the two services on the same machine is also removed, rendering the still-running service useless. How can I configure the cluster to keep the IP address up? The only way I found so far was to assign a different virtual IP address to each of the service not needing a disk (not implemented in the following cluster.conf).

The only way to make this work was to give the services not needing a disk their own virtual IP addresses. Is that the way it is supposed to work?

cluster.conf now looks like this:

<?xml version="1.0" ?>
<cluster config_version="1" name="cluster">
  <fence_daemon clean_start="0" post_fail_delay="0" post_join_delay="3"/>
  <cman shutdown_timeout="10000"/>
  <clusternodes>
    <clusternode name="node1" nodeid="1" votes="1">
      <fence>
        <method name="1">
          <device name="device1"/>
        </method>
      </fence>
    </clusternode>
    <clusternode name="node2" nodeid="2" votes="1">
      <fence>
        <method name="1">
          <device name="device2"/>
        </method>
      </fence>
    </clusternode>
    <clusternode name="node3" nodeid="3" votes="1">
      <fence>
        <method name="1">
          <device name="device3"/>
        </method>
      </fence>
    </clusternode>
  </clusternodes>
  <fencedevices>
      <fencedevice agent="fence_ilo" ipaddr="10.0.24.101" login="admin" name="device1" passwd="password"/>
      <fencedevice agent="fence_ilo" ipaddr="10.0.24.102" login="admin" name="device2" passwd="password"/>
      <fencedevice agent="fence_ilo" ipaddr="10.0.24.103" login="admin" name="device3" passwd="password"/>
  </fencedevices>
  <rm>
    <failoverdomains>
      <failoverdomain name="domain1" nofailback="0">
        <failoverdomainnode name="node1" priority="1"/>
      </failoverdomain>
      <failoverdomain name="domain2" nofailback="0">
        <failoverdomainnode name="node2" priority="1"/>
      </failoverdomain>
    </failoverdomains>
    <resources>
      <ip address="10.0.24.111" monitor_link="1"/>
      <ip address="10.0.24.112" monitor_link="1"/>
      <ip address="10.0.24.113" monitor_link="1"/>
      <ip address="10.0.24.114" monitor_link="1"/>
    </resources>
    <service autostart="1" exclusive="0" name="disk1" recovery="restart" domain="domain1">
      <ip ref="10.0.24.111"/>
      <script file="/etc/init.d/disk1" name="disk1"/>
      <fs device="/dev/VolGroup10/LogVol10" force_fsck="0" force_unmount="1" fstype="ext3" mountpoint="/mnt/lun1" name="lun1" self_fence="1"/>
      <lvm lv_name="LogVol10" name="VolGroup10/LogVol10" vg_name="VolGroup10"/>
    </service>
    <service autostart="1" exclusive="0" name="nodisk1" recovery="restart" domain="domain1">
      <ip ref="10.0.24.112"/>
      <script file="/etc/init.d/nodisk1" name="nodisk1"/>
    </service>
    <service autostart="1" exclusive="0" name="disk2" recovery="restart" domain="domain2">
      <ip ref="10.0.24.113"/>
      <script file="/etc/init.d/disk2" name="disk2"/>
      <fs device="/dev/VolGroup20/LogVol20" force_fsck="0" force_unmount="1" fstype="ext3" mountpoint="/mnt/lun2" name="lun2" self_fence="1"/>
      <lvm lv_name="LogVol20" name="VolGroup20/LogVol20" vg_name="VolGroup20"/>
    </service>
    <service autostart="1" exclusive="0" name="nodisk2" recovery="restart" domain="domain2">
      <ip ref="10.0.24.114"/>
      <script file="/etc/init.d/nodisk2" name="nodisk2"/>
    </service>
  </rm>
</cluster>