HA / Cluster / slots

[naymar27]

Hi everyone,

I've got an issue on my datacenter. When a server is down, the workload on that server does not move to the others servers (2). HA doesn't work properly. How can I do to solve this issue? I hope the screenshot will help you. Thanks

[a_p_]

It looks like some of the VMs have reservations (memory and/or CPU) which increases the slot size, and therefore reduces the number of available slots. Since there are more slots used than available, it also seems that Admission Control is disabled on the cluster. Unless the VM's need these reservations, I'd suggest you remove them, and also check the cluster's HA settings.

André

[naymar27]

Thanks !!

Yeah the Admission Control is disable. I did cause it was impossible for me to work when it was activated.

If a remove the memory reservation is it possible for the slot size to reduce or I should only remove the VM or is there another way of reducing the slot size?

[a_p_]

As soon as all reservations are removed from the VMs, the slots will be recalculated (no reboot etc. required) based on the default slot settings. Once HA has available free slots it should work as expected, and restart VMs in case of a host failure.

As of vSphere 5.5 there's also an advanced option to configure fixed values for the slot size calculation. However this should only be done in specific cases, e.g. when you are low on physical memory, but have a VM which requires a reservation (due to technical or support reasons).

André

[naymar27]

Hello a.p.,

Thanks for your help. Indeed, it was really helpful. But I still have a problem regarding that.

The HA doesn't still work.

I could this screenshots

[depping]

I would also recommend to change the admission control policy to "percentage based" as that more than likely would have prevented you from hitting this situation in the first place. The slot policy takes the worst possible situation in to account (for ALL HA details go here: ha.yellow-bricks.com) and a high reservation will skew the number of available slots.

[naymar27]

Thanks