[ovirt-users] The roles of DRDB and Gluster in oVirt for High Availability

[OvirtAndKvm]

    If anyone has the knowledge and time, I would be interested to
read about if DRDB is used with oVirt, and since I have read that
Gluster is used with oVirt, but just how does Gluster help provide
High Availability?

I would like to set up a two physical server HA solution (similar to
or using the Self Hosted engine).  Where each server is monitoring
the other, using block replication so that each keep a copy of the
other server's running virtual machine's virtual storage (e.g. virtual
hard disks), and I guess for HA it would require both physical servers
to be running the same virtual machine instance, where the production
or active VM (memory) is being replicated into the secondary or
standby server.

However my actual needs would easily be supported by a simpler
approach, "oVirt now has the scheduling capability to flag individual
VMs for high availability. In the event of a host failure, these VMs
are rebooted on an alternate hypervisor host", however I don't know
how the VM would be rebooted on another host if the [shared] storage
device failed. Hence my interest in DRDB for block replication using a
minimum of two storage devices.

Single shared storage creates a single point of failure, so storage
must also be replicated. In a two physical server model, both physical
servers would provide storage and allow for storage to be
replicated.  Ideally, each physical server would have two storage
areas, one that is a replication of the other servers storage area,
and one which the other server is replicating.

Is there a way for one physical server to hourly or nightly replicate
its virtual machine's storage to the other physical server ?  Kind of
like if a rsync was set up in cron?, but a bit more of a sophisticated
solution. 

http://searchservervirtualization.techtarget.com/tip/Power-management-a-must-for-oVirt-high-availability
To build oVirt high availability, you need a minimum of two hosts, as
well as a shared storage platform [1]. You also need to configure
power management [2] on the hosts.

http://www.linbit.com/en/company/news/333-high-available-virtualization-at-a-most-reasonable-price
Using DRBD and Pacemaker with oVirt...

http://blog.gluster.org/2013/09/ovirt-3-3-glusterized/
http://rehdat.blogspot.com.au/2013/04/rhev-31-active-direcotry-vms-high.html


I read the below information but it is too a high level to explain how
HA is achieved.
http://www.ovirt.org/OVirt_3.0_Feature_Guide#High_availability 


HIGH AVAILABILITY 



Allows critical VMs to be restarted on another host in the event of
hardware failure with three levels of priority, taking into account
resiliency policy. 



	*  Resiliency policy to control high availability VMs at the cluster
level. 
	*  Supports application-level high availability with supported
fencing agents.
http://community.redhat.com/blog/2014/03/ovirt-3-4-unveiled/



Links:
------
[1]
http://searchstorage.techtarget.com/answer/Shared-storage-and-SAN-differences
[2]
http://searchdatacenter.techtarget.com/definition/intelligent-power-management-IPM

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