Want to predict which host will become your high availability master?
According to Duncan Epping's deep dive here
The host that is participating in the election with the greatest number of connected datastores will be elected master. If two or more hosts have the same number of datastores connected, the one with the highest Managed Object Id will be chosen. This however is done lexically; meaning that 99 beats 100 as 9 is larger than 1
So the host with the most datastores should win
And if they have equal stores
The host with the highest moid should win.
Test A
Here I have 4 hosts.
Host 3 has 4 datastores every other host has 1
Host3 should become the ha master
Currently there is no HA master as it is off
Turning on HA
It installed on host 1 first so it came up first so it was the master.
This is after it finished
So the first host to have ha installed is the one that gets to be the master
TestB
What if we bump that one off?
Will #3 then become the master?
Yes. As predicted #3 is the master
TestC
Now the other 3 hosts have the same number of datastores.
So if we bump off 3 then when one will be the master?
Lets look at the MOID
Host 1 should be the master since it has a moid of 98. remember lexically 94 > 103
Host 3 moid 98 is already the master so it doesn’t count in our guess of who the master will be.
Host 3 moid 98 is already the master so it doesn’t count in our guess of who the master will be.
Bump off #3
Number 1 is the master
Yes. As predicted #1 is the master
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