There are usually a few ways, but as usual "it depends" - different RAID controllers use different methods.
Assuming these are windows boxes, often there is a WMI query you can call to get the status; on others it may be an SNMP trap; still others you may be able to use an event log alert, or a log filter. Dell servers also have DRAC controllers that may be able to give you status information.
You would need to say what sort of RAD controller you have and which windows OS, before we can go much further....
Kaseya people will probably tell you that KNM version 5 can do this out-of-the-box. Well, thats great, but KNM isn't available within Kaseya as yet (there is a standalone version available) so KNM5 isn't usually a viable option.