The roles of DRDB and Gluster in oVirt for High Availability

20 Aug 2014

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

I would like to set up a two physical server HA s=
olution (similar to
or using the Self Hosted engine).=C2=A0 Where each=
 server is monitoring
the other, using block replication so that eac=
h keep a copy of the
other server's running virtual machine's virtua=
l storage (e.g. virtual
hard disks), and I guess for HA it would requ=
ire both physical servers
to be running the same virtual machine ins=
tance, 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 h=
as the scheduling capability to flag individual
VMs for high availabi=
lity. In the event of a host failure, these VMs
are rebooted on an al=
ternate hypervisor host", however I don't know
how the VM would be r=
ebooted on another host if the [shared] storage
device failed. Hence =
my interest in DRDB for block replication using a
minimum of two sto=
rage devices.

Single shared storage creates a single point of f=
ailure, so storage
must also be replicated. In a two physical server=
 model, both physical
servers would provide storage and allow for st=
orage to be
replicated.=C2=A0 Ideally, each physical server would have=
 two storage
areas, one that is a replication of the other servers s=
torage area,
and one which the other server is replicati=
ng.

Is there a way for one physical server to hourly or night=
ly replicate
its virtual machine's storage to the other physical ser=
ver ?=C2=A0 Kind of
like if a rsync was set up in cron?, but a bit mo=
re of a sophisticated
solution.=20

http://searchservervirtual=
ization.techtarget.com/tip/Power-management-a-must-for-oVirt-high-availa=
bility
To build oVirt high availability, you need a minimum of two h=
osts, as
well as a shared storage platform [1]. You also need to con=
figure
power management [2] on the hosts.

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

http://blo=
g.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 ho=
w
HA is achieved.
http://www.ovirt.org/OVirt_3.0_Feature_Guide#H=
igh_availability=20

HIGH AVAILABILITY=
=20

Allows critical VMs to be restarted on another ho=
st in the event of
hardware failure with three levels of priority, t=
aking into account
resiliency policy.=20

	*  R=
esiliency policy to control high availability VMs at the cluster
lev=
el.=20
	*  Supports application-level high availability with supported=

fencing agents.
http://community.redhat.com/blog/2014/03/ovirt-=
3-4-unveiled/

Links:
------
[1]
htt=
p://searchstorage.techtarget.com/answer/Shared-storage-and-SAN-differenc=
es
[2]
http://searchdatacenter.techtarget.com/definition/intelli=
gent-power-management-IPM

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<body>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 Glu=
ster is used with oVirt, but just how does Gluster help provide High Ava=
ilability?<br><br>I would like to set up a two physical server HA soluti=
on (similar to or using the Self Hosted engine).  Where each server=
 is monitoring the other, using block replication so that each keep a co=
py 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 produ=
ction or active VM (memory) is being replicated into the secondary or st=
andby server.<br><br>However my actual needs would easily be supported b=
y a simpler approach, "oVirt now has the scheduling capability to flag i=
ndividual VMs for high availability. In the event of a host failure, the=
se VMs are rebooted on an alternate hypervisor host", however I don't kn=
ow 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 m=
inimum of two storage devices.<br><br>Single shared storage creates a si=
ngle point of failure, so storage must also be replicated. In a two phys=
ical 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.<br><br>Is t=
here a way for one physical server to hourly or nightly replicate its vi=
rtual machine's storage to the other physical server ?  Kind of lik=
e if a rsync was set up in cron?, but a bit more of a sophisticated solu=
tion. <br><br>http://searchservervirtualization.techtarget.com/tip/Power=
-management-a-must-for-oVirt-high-availability<br>To build oVirt high av=
ailability, you need a minimum of two hosts, as well as a <a href=3D"http:=
//searchstorage.techtarget.com/answer/Shared-storage-and-SAN-differences=
">shared storage platform</a>. You also need to configure <a href=3D"http:=
//searchdatacenter.techtarget.com/definition/intelligent-power-managemen=
t-IPM">power management</a> on the hosts.<br><br>http://www.linbit.com/e=
n/company/news/333-high-available-virtualization-at-a-most-reasonable-pr=
ice<br>Using DRBD and Pacemaker with oVirt...<br><br>http://blog.gluster=
.org/2013/09/ovirt-3-3-glusterized/<br>http://rehdat.blogspot.com.au/201=
3/04/rhev-31-active-direcotry-vms-high.html<br><br><br>I read the below =
information but it is too a high level to explain how HA is achieved.<br=
...
http://www.ovirt.org/OVirt_3.0_Feature_Guide#High_availability <br><h3>=
<span class=3D"mw-headline" id=3D"High_availability">High availability <=
/span></h3><p>Allows critical VMs to be restarted on another host in the=
 event of hardware failure with three levels of priority, taking into ac=
count resiliency policy. </p><ul><li> Resiliency policy to control high =
availability VMs at the cluster level. </li><li> Supports application-le=
vel high availability with supported fencing agents.</li></ul><br>http:/=
/community.redhat.com/blog/2014/03/ovirt-3-4-unveiled/<br><br></body></h=
tml>
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OvirtAndKvm

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