VMware Cloud Community
aemonzon
Contributor
Contributor
‎05-06-2019 06:45 AM

Question about Failover Slots number

Hello guys. I have some doubts about HA slot calculation & sizes. Last week one of our 5.5 ESXi hosts in a 2 node cluster failed. Unfortunately none of the VMs were restarted by HA on the other host

I was trying to figure out why this happened and I came across with the following. The "Available Slots" being 0 means that I won't be able to power-on more VMs on the cluster. The "Failover slots" value is 4. Does this mean that in case of failure HA will only be able to failover 4 VMs? Cluster tolerates failure is set to 1 host

pastedImage_0.png

0 Kudos
2 Replies
lukebes1010
Enthusiast
Enthusiast
‎05-06-2019 08:32 AM

According to https://docs.vmware.com/en/VMware-vSphere/5.5/vsphere-esxi-vcenter-server-55-availability-guide.pdf :

When you select the Host Failures Cluster Tolerates admission control policy, the Advanced Runtime Info pane appears in the vSphere HA section of the cluster's Monitor tab in the vSphere Web Client. This pane displays the following information about the cluster:

  • Total slots in cluster. The sum of the slots supported by the good hosts in the cluster.
  • Used slots. The number of slots assigned to powered-on virtual machines. It can be more than the number of powered-on virtual machines if you have defined an upper bound for the slot size using the advanced options. This is because some virtual machines can take up multiple slots.
  • Available slots. The number of slots available to power on additional virtual machines in the cluster. vSphere HA reserves the required number of slots for failover. The remaining slots are available to power on new virtual machines.
  • Failover slots. The total number of slots not counting the used slots or the available slots.
  • Total number of powered on virtual machines in cluster.
  • Total number of hosts in cluster.
  • Total good hosts in cluster. The number of hosts that are connected, not in maintenance mode, and have no vSphere HA errors.
0 Kudos
a_p_
Leadership
Leadership
‎05-06-2019 09:44 AM

I've seen such HA slot calculation a couple of times, and in most cases the memory reservation (one one, or more VMs) which causes the memory slot size of 24754MB has been set non-intentionally. Removing the reservation (unless it's really required) will help.


André

0 Kudos