If you use storage providers, the vCenter Server can collect status characteristics for physical storage devices and display this information in the vSphere Web Client.
The status information includes events and alarms.
Events indicate important changes in the storage configuration. Such changes might include creation and deletion of a LUN, or a LUN becoming inaccessible due to LUN masking.
Alarms indicate a change in storage system availability. For example, when you use profile-based storage management, you can specify virtual machine storage requirements. When changes to underlying storage occur that might violate the storage requirements of the virtual machine, an alarm gets triggered.
For more information about events and alarms, see the vSphere Monitoring and Performance documentation.
Thin-provisioned LUNs have special reporting requirements. For information about space monitoring on thin-provisioned LUNs, see Array Thin Provisioning and VMFS Datastores.