High availability - host failure number

fred974

Hi,

I have enabled HA in my pool of 4x host running xe pool-ha-enable heartbeat-sr-uuids=<UUID>.

QUESTION: Do I also need to set the maximum host failure number? As I have 4x hosts, am I correct to think that I will need to set it to 3?

[09:31 uk ~]# xe pool-ha-compute-max-host-failures-to-tolerate
4

Do I simply leave everything as is or do I manually set the value to 3 with xe pool-param-set ha-host-failures-to-tolerate=**3** uuid=<Pool_UUID>

Thank you

henri9813

Hello @fred974

Did you find your answer ?

I don't understand clearly how a 4 nodes pool can tolerate 4 nodes dead.

nikade

Think of it like this:

If you have 4 hosts, each host maximum usage will be 25% of the total - How much of that % do you want to reserve in case of a failed host?
Personally, I'd like to have the number set to 1 host (25%) because that means im able to use 3 hosts and the 4th hosts resources would be reserved in case of a failure.

henri9813

Hello, @nikade

Yeah i think like this already, but i'm surprised by the result of the calcul.

I should i have either: 3 nodes which can die, or "1", but i should not have the same number right ?

in my case, i run the command in a 3 hosts cluster and it return me 3 as value. which disturb me.

Best regards,