Datastore cluster are very similar to host clusters, just for an example you have a vm on one host that host goes down that VM goes down. You have a VM on a cluster and one host goes down the VM can be moved with DRS or HA and everything is ok. With a datastore cluster, you combine multiple datastore into one big cluster and place your VMs not directly on the datastore but on the cluster. Essentially a “cluster” of datastores, pretty simple concept overall it is important to note there a multiple file systems for these datastore. For one there is VMFS, virtual machine file system, this file system is used by FC, FCoe, SAN, and local disk on your host in vCenter. It has a set of features such as being able to have multiple hosts write to the same storage device at the same time, allowing you to increase the size of the datastore with hosts running, then finally VMFS supports on-disk lock which prevents other hosts from accessing the VMs file if it’s not running on one of those hosts, if the host the VM is running on does go down this locked is disabled so other hosts will be able to access the files, such as if the VM is moved with HA after the initial host failure, so there is a fail-safe in place, this post was a bit shorter than normal. As always feel free to comment with questions!