[ovirt-users] dns vm and ovirt

[Christopher Cox]

On 03/16/2018 07:58 AM, Nathanaël Blanchet wrote:
> Hi all,
> 
> I'd need some piece of good practice about dealing a DNS server in or 
> out of ovirt.
> Until now we never wanted to integrate the DNS vm into ovirt because of 
> the strong dependency. if the DNS server fails for any reason, it 
> becomes difficult ot join the webadmin (except with a static etc hosts) 
> and the nodes may become unvailable if they had been configured with fqdn.
> We could consider a DNS failover setup, but in a self hosted engine 
> setup (and more globally an hyperconverged setup) , it doesn't make 
> sense of setting up a stand alone DNS vm outside of ovirt.
> 
> So what about imitating engine vm status in a hosted engine setup? Is 
> there a way to install the DNS vm outside of ovirt but on the ovirt host 
> (and why not in a HA mode)?
> Second option could be installing the named service on the hosted engine 
> vm?
> 
> Any suggestion or return of experience would be much appreciated.
> 

You are wise to think of this as a dependency problem.  When dealing 
with any "in band" vs. "out of band" type of scenario you want to 
properly address how things work "without" the dependency.

So.. for example, you could maintain a static host table setup for your 
ovirt nodes.  Thus, they could find each other without DNS.  Also, those 
nodes might have an external DNS configured for lookups (something you 
don't own) just so things like updates can happen.

There are risks to everything.  Putting key (normally) out of band 
infrastructure into your oVirt, including the engine, always involves 
more risk.

With that said, if you think about you key infrastructure being as a 
separate oVirt datacenter, it would have things like the "static host" 
maps and such.  Some of the infrastructure VMs housed there could 
include the engine for the "general" datacenters (the ones not providing 
VMs for key infrastructure).  This these "general" purpose datacenters 
would house the normal VMs and use potentially VMs out of the 
"infrastructure" datacenter.  Does that make sense?

It's not unlike how a lot of cloud providers operate.  In fact, one well 
known provider used to house their core cloud infrastructure in VMware 
and use "cheaper" hypervisors for their cloud clients.

Summary:
static confs for infrastructure ovirt datacenter containing key core 
infrastructure VMs (including things like DNS, DHCP, Active Directory, 
and oVirt engines) used by general purpose ovirt datacenters.

Obviously the infrastructure datacenter becomes very important, much 
like your base network and should be thought of as "first" priority, 
much like the network.  And much like the network, depends on some 
kickstarter static configs.