Disk Monitors? Linux or ESX?

Hello,
I'm a little confused about using OPManager in the case where I have an ESX or Linux server. I'm not sure how to go about setting up, let's say, disk monitors. I'm using HP DL380 servers as ESX and one as Linux Openfiler and I'd like to be able to report if I have a disk failure in one of the RAID configs but I'm not sure how to go about this. Should I configure some kind of agent on these servers or is there something I can do directly with SNMP or SNMP traps. I'm a little new at OPManager but I've been able to configure most of my Windows Servers without any issues. Any help would be greatly appreciated.

Thanks