Placement groups

The relative placement of a group of VMs across the underlying physical hardware is controlled via their placement group. A placement group is a logical grouping of VMs, and has an associated placement strategy which describes how the VMs are scheduled across the physical hardware relative to eachother. To change a VM's placement group it must be stopped.

Placement strategies

Currently, there is one placement strategy: spread.

Spread

The "spread" placement strategy specifies that VMs in a given placement group are each scheduled to different physical hosts.

A placement group with the spread placement strategy can contain at most 5 VMs.

The VMs are scheduled in a hard anti-affinity manner: under no circumstances shall two VMs in the same placement group be scheduled to the same physical host. For example, if there are n physical hosts and you try to add the n+1th VM to a placement group, it shall not be scheduled.