[ovirt-users] dns vm and ovirt

[Christopher Cox]

On 03/16/2018 12:28 PM, Nathanaël Blanchet wrote:
> Thanks for precious advices!
> 
> So  it means that people who thought about hosted engine feature didn't 
> get into your philosophy of running the engine into a second datacenter

Again, strictly a "risk" thing.  Hosted engine is by definition a 
"chicken and egg" thing.  It's great for learning and for lab... but if 
you're going to run production, I'd at least consider the latter option 
I presented.

With that said, we run dedicated engines today, not hosted.  Remember, 
ovirt nodes run even while the engine is down.  So you can tolerate an 
engine outage for a time period, just can't have reliability in case of 
node failures, etc.  So for us, most of the risk is in rebuilding a new 
engine if we have to... but certainly considered a "rare" case.

Putting key infrastructure inside the very thing that needs the key 
infrastructure to run is just fraught with problems.

Everything has costs and typically, the more robust/reliable your setup, 
the more it's going to cost.  I just wanted to present an "in between" 
style setup that gives you more reliability, but perhaps not the "best", 
while keeping costs way down.

To me, if you're running any datacenter cluster (for example), you need 
to have a minimum of 3 nodes.  People might not like that, but it's my 
minimum for reliability and flexibility.

So... if wanted to use VMs for core infrastructure, that's 3 nodes. 
That core infrastructure datacenter might have a hosted engine, but 
likely also has "static definitions".  It's part of the "core", at least 
several parts of it are.  But the idea is it could hold: DNS, DHCP, 
Active Directory/LDAP, files shares (even storage domains for other 
datacenters), etc.  Obviously a "core" failure is a "core" failure and 
thus needs the same treatment as whatever you consider to be "core" today.

(thus on total "outage" bring up, you bring up the core, which now
includes this core infrastructure datacenter... your core "tests" are 
run to verify, and then the rest is brought up)

Then each general production datacenter cluster would have 3 nodes with 
the engine(s) being a VM(s) off the infrastructure datacenter using core 
infrastructure off that infrastructure datacenter as well.  Again, this 
is very much like most cloud service providers today.

Again, just ideas, mainly thinking on the "cheap", though some might not 
think so (you'll just have to trust me, what I'm presenting here is
incredibly cheap for the reliability and flexibility it provides).

Just my opinion.