[one-users] Private cloud with Front-end on Virtual MAchine HA

[Daniel Dehennin]

Giancarlo De Filippis <gdefilippis at ltbl.it> writes:

> I hope (like you) that someone (users or OpenNebula Team) have best
> practices on how to run OpenNebula in a VM.

Hello,

The ONE frontend VM can not manage itself, you must use something else.

I made a test with pacemaker/corosync and it can be quite easy[1]:

#+begin_src conf
primitive Stonith-ONE-Frontend stonith:external/libvirt \
        params hostlist="one-frontend" hypervisor_uri="qemu:///system" \
        pcmk_host_list="one-frontend" pcmk_host_check="static-list" \
        op monitor interval="30m"
primitive ONE-Frontend-VM ocf:heartbeat:VirtualDomain \
        params config="/var/lib/one/datastores/one/one.xml" \
        op start interval="0" timeout="90" \
        op stop interval="0" timeout="100" \
        utilization cpu="1" hv_memory="1024"
group ONE-Frontend Stonith-ONE-Frontend ONE-Frontend-VM
location ONE-Frontend-run-on-hypervisor ONE-Frontend \
        rule $id="ONE-Frontend-run-on-hypervisor-rule" 40: #uname eq nebula1 \
        rule $id="ONE-Frontend-run-on-hypervisor-rule-0" 30: #uname eq nebula3 \
        rule $id="ONE-Frontend-run-on-hypervisor-rule-1" 20: #uname eq nebula2
#+end_src
        
I have troubles with my cluster because my nodes _and_ the ONE frontend
needs to access the same SAN.

My nodes have two LUNs over multipath FC (/dev/mapper/SAN-FS{1,2}), they
are both PV of a cluster volume group (cLVM) with a GFS2 on top.

So I need:

- corosync for messaging
- dlm for cLVM and GFS2
- cLVM
- GFS2

I add the LUNs as raw block disks to my frontend VM and install the
whole stack in it, but I'm facing some communication issues, and manage
to solve somes[3].

According to the pacemaker mailing list, having the nodes _and_ a VM in
the same pacemaker/corosync cluster ”sounds like a recipe for
disaster”[2].

Hope this will help you have a picture of the topic.

Regards.

Footnotes: 
[1]  http://clusterlabs.org/doc/en-US/Pacemaker/1.1-crmsh/html-single/Clusters_from_Scratch/index.html

[2]  http://oss.clusterlabs.org/pipermail/pacemaker/2014-November/023000.html

[3]  http://oss.clusterlabs.org/pipermail/pacemaker/2014-November/022964.html

-- 
Daniel Dehennin
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