Q: What are the important limitations in the VMware vSphere Storage Appliance?

The VSA doesn't support memory overcommit.

The VSA, once installed, prohibits adding additional storage to a VSA cluster.

The VSA creates a useable partition that's equivalent to the amount of disk space in the server that contains the least quantity of disk space.

The VSA isn't intended to be installed onto existing ESXi hosts; it prefers a "green field" installation onto essentially unconfigured hardware.ESXi hosts can't run VMs before creating the VSA cluster.

The VSA, in combination with VMware's RAID requirements for locally attached storage, requires a 75 percent storage overhead for redundancy.This requirement means only 25 percent of deployed storage is actually available for use.

The VSA can be configured in a two- or three-server configuration that, once installed, can't be altered.

VMware suggests you don't run vCenter Server within VSA as a VM because the loss of a datastore could prevent access to the VSA Manager. As aresult, an additional and separate physical computer or VM is required to run vCenter Server and the VSA Manager.

The VSA reserves 33 percent of CPU and memory resources on a three-host cluster and 50 percent of CPU and memory resources on a two-host clusterfor high availability admission control.