As you know, VMware vSphere has really nice features. One of then is the VMware HA or VMware High Availbility feature. With this, it is possible to build a high availbility Cluster for virtual maschines. Any virtual Machine in that cluster are protected for Hosts crashes.
The HA Feature monitors all ESX-Hosts in the Cluster and restart any virtual maschine on other ESX-Server if one or more ESX-Servers are crashing. So the virtual machines are back and running in a few minutes.
A VMware Cluster can be build with at least max. 32 ESX-Hosts. You must configure it by the vCenter Server, but pretty nice is, that the VMware HA Feature works without the vCenter Management Server. This means that the ESX-Host is montoring itself and all other ESX-Hosts over heartbeats.
All Server do it?... Not all!
In a VMware HA Cluster are max. five ESX-Server primary Hosts. All other ESX-Hosts will be secondary Hosts. Only the primary Hosts will be have Information about the whole Cluster. The secondary Host does not have that Information. But in a kind of failure, a secondary Hosts can be promoted to a primary Node by any primary Node.
In the normal Szenario, if one primary Host goes down, the other primary Node realize that over the heartbeat and promote a secondary Hosts to a primary Host.
But what happend, if all primary Hosts goes down at the same time? Now the Cluster has a problem, that no ESX-Hosts has Information about the whole Cluster and can´t promote any Hosts to a primary state. Did you think that this szenario are infrequent? We have seen this really often.
One Example is, when you build a Cluster over two locations. The only secured way for that szenario is, to build up a Cluster with max. of 8 ESX-Hosts, so you can sure, that at least one Host per location is a primary host.
But what can you do if you want to build a cluster with more than 8 Hosts? Are you sure that you have primary Nodes on all Locations? Where can you seen this? The vCenter Client dosn´t show you this Information.
In many Project we are asked which ESX-Server in a VMware Cluster are active (primary) and which one was passive (secondary). So we build a little Tool that display the primary Nodes in a VMware Cluster what we named MCS-ViewHA. With that, you can see which ESX-Node is a primary Node.
You can Download this free Tool from our Website.
http://www.mightycare.de/downloads/mcs_viewha
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