VCenter Server installed as a VM within one of the ESXi servers it is managing???

[Threxx]

Hi all. I'm new to the world of VSphere... still in my evaluation period.

I've got only one ESXi server running at the moment but plan to add a second one later for high availability, vmotion, general capacity increases, etc. They are/will be running ESXi on internal storage and running the VMs on a shared SAN.

Today I installed VCenter Server 4 on a low end server/desktop I had laying around running XP Pro x64.

As I was installing it I read the install guide and to my surprised it seemed to recommend that I install VCenter Server 4 as a VM on my ESXi host.

Now maybe I've just been spending too much time configuring my new Lefthand SANs which require a 'witness' during failover from one SAN to another... but I was under the impression that VCenter Server wasn't just meant for host configuration, but was also designed to act as a 'witness' or to allow for quorum whenever a failure scenario occurred on one of my ESXi hosts. I also noticed the VCenter Server has a 'heartbeat' port, which I assume would be used for the heartbeats of the ESXi hosts, but maybe it's only used for 'linked mode' with other VCenter Servers (which I was intending to only use one since this is a small scale installation) I was also under the impression that it would be fairly useful in restoring a downed or corrupted ESXi host.

So my question is, if my ESXi host dies, and it's where I have VCenter Server installed, then won't high availability be unable to work? I'm assuming there will be other issues with me being unable to access VCenter Server while I have a downed ESXi host, too, like greater difficulty getting the ESXi back up?

Maybe I'm misunderstanding the purpose of the VCenter Server... maybe it's not something that's needed for HA, recovery, etc and just acts as a configuration tool before anything goes wrong? Or maybe I misunderstood the installation guide and while they recommend I install VCenter Server on an ESX box... they don't want that ESX box to be part of the group that the server is managing?

Lastly, if in fact they are recommending I install this on one of the ESXi hosts it is managing... would I ideally be installing this to local storage on the server (where I have ESXi installed) or on the SAN (where all my other VMs are installed)... or is it just personal preference?

Thanks!!

[MattG · Accepted solution]

When you add hosts to an HA enabled vCenter cluster, an HA agent is installed on it. This agent is what actually performs the HA functions. While vCenter is needed to add new hosts to a cluster and configure certain vCenter specific settings, the HA agents are self sufficient and can manage HA failover while vCenter is offline.

You should install the vCenter VM on SAN storage so that it can use the vMotion, sVmotion, DRS, HA, etc features that require SAN.

-MattG

If you find this information useful, please award points for "correct" or "helpful".

[AndreTheGiant]

See also:

Andre

[AntonVZhbankov]

>also designed to act as a 'witness' or to allow for quorum whenever a failure scenario occurred on one of my ESXi hosts

Quorum is Microsoft term, and there is no quorum in vSphere. vCenter performs only initial configuration for HA (or reconfiguration), but since configuration is done HA is on its own. So if ESXi host with vCenter VM fails HA will restart vCenter.

All VMs you want to protect with HA MUST be on SAN. If host fails how would you access its local storage?

---

MCSA, MCTS Hyper-V, VCP 3/4, VMware vExpert '2009

http://blog.vadmin.ru

[Threxx]

My experience with the term 'quorum' most recently was with HP/Lefthand SANs which require a failover manager to provide quorum.

I've never had any question where I was going to place my VMs since HA obviously requires shared storage... I just wasn't sure where to place vCenter Server. Considering the ESXi host is installed on local storage (despite the fact that my servers will boot off an ISCSI target)... I didn't know if there were some considerations I hadn't made.

[Josh26]

The closest thing to a "witness" is your default gateway, which your two servers will send hearbeats to regularly. If the two servers cannot see each other, the one that can still see the gateway will be the one that wins.

[Threxx]

Interesting. I actually didn't set any default gateway (or DNS servers) on my ESXi hosts since they're segregated into a VLAN with none of the above available. I suppose for this and potentially other reasons I should make both services available to them?