In VMware, the storage space is conceived as a datastore. The datastore is a virtual representation of the storage resources on which VMs, templates, or ISO images are stored. The datastore hides the complexity of the different technologies and storage solutions by offering the ESX server a uniform model no matter what storage has been implemented. Datastore types are VMFS and NFS.
A datastore cluster, also called a pool of datastores (POD), is a collection of datastores grouped to form a single entity as illustrated in Figure 3.15. When a datastore cluster is created, Storage DRS can be used.
Figure 3.15. Pool of datastores (POD).
A datastore cluster can consist of volumes from different storage arrays (in terms of performance and volume), and different VMFS can be mixed (VMFS-3 and VMFS-5), but this is not generally recommended. The mix of VMFS and NFS volumes in a datastore cluster is not supported.