Rob van My digital life


VMware: HA Advanced Runtime Info

A few minutes ago I took a quick look at the summary tab of my cluster. In the VMware HA box I noticed the following line: "Current Failover Capacity: 0 hosts"...

After opening the "HA Advanced Runtime Info" link it turns out I had only 80 HA Slots in my cluster (256 MHz, 2 vCPU's and 2048MB RAM). After some research I detected 1 VM with a memory reservation (2048MB), after I removed the reservation the available slots jumped from 80 to 329 🙂

The HA box now say "Current Failover Capacity: 4 hosts". Just another example why you don't want to use reservations in a vSphere cluster.

For more details and technical background regarding VMware HA I suggest reading the "HA Deepdive" article written by Duncan Epping @


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  1. Ha ha, I did something similar, went from 15 slots to 222, all due to a reservation for a SQL box of 10000Mb of RAM!

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