You can monitor the RAID status, but you'll need to set up a custom poller (Universal Device Poller). It varies for different vendors. For example, for Dell, you will need to have OpenManage on the server, then you can set up a custom poller to collect array state (which I think is 1.3.6.1.4.1.674.10893.1.20.130.4.1.4).
I watch for disk failures by sending snmp traps back to the orion server and forwarding those with email.
Dell:StorageManagement-MIB:storageManagementEvent.0.904StorageManagement-MIB:storageManagementEvent.0.903StorageManagement-MIB:storageManagementEvent.0.901HP:CPQHLTH-MIB:compaq.0.3008CPQHLTH-MIB:compaq.0.3046CPQHLTH-MIB:compaq.0.3034CPQHLTH-MIB:compaq.0.3025CPQHLTH-MIB:compaq.0.3029CPQHLTH-MIB:compaq.0.3047