I was yesterday trying to establish a relation between Datastore and Virtual Machine, ESXi host
If you look below, it was not clear for me based on the naming convention.
Naming convention do not actually confirms to which cluster or host these datastores are associated.
This is where the use of folder comes to picture. In fact I feel this is one of the used cases for folders.
Create a folder based on cluster name and drag and drop the luns associated with the cluster. Now see below how well it is arranged and you can easily set alarm on entire cluster in datastore view.