A VSA cluster created with vSphere Storage Appliance 1.0 does not support memory overcommitment. VMX swapping is enabled by default and swapping to VSA datastores can make the cluster unstable, and as a result, virtual machines might begin powering off.

To prevent virtual machine downtime, do not overcommit memory in the VSA cluster. For each virtual machine in the VSA cluster, reserve the same amount of memory that is allocated to that virtual machine and disable the machine from swapping to the VSA datastores. Such a configuration ensures that all virtual machines running on an ESXi host in the VSA cluster do not use more memory than that available on the host, and do not attempt to perform VMX swapping.

For a VSA cluster that has HA enabled, the cluster reserves additional host memory to support the restart of virtual machines from a failed peer host. In a 2-member VSA cluster, HA reserves 50 percent of the reserved memory of each host for the restart of a failed-over virtual machine. Similarly, in a 3-member VSA cluster, HA reserves 33 percent of the reserved memory of each host for the restart of a failed-over virtual machine.

If you attempt to power on a virtual machine that exceeds the reserved memory threshold, the operation fails. Due to the memory threshold of an ESXi host, it is possible that not all virtual machines can be restarted on a running host in the event of a host failure.