The PERC5 and PERC6 are SAS (Serial Attached SCSI) RAID controllers from DELL which are actually special LSI MegaRAID SAS controllers.
If you're running Linux there are exactly two ways of administrating your PERC: Either using DELL's OpenManage Server Administrator (OMSA) or struggling with the cryptic tools supplied by LSI. The former is a (some would say bloated) Java-based GUI managing and monitoring suite whereas the latter is a very small command line utility. If you're using your DELL machine as a server it's often not very desirable to use have a web server running for the administration and monitoring tool – guess why. So this leaves you fighting with the LSI command line tool which is actually very powerful but poorly documented.
On this page you'll find information on the PERC itself as well as how to manage and monitor your controller using the the LSI MegaCli command line tool (see Emergency Cheat Sheet).
This cheat sheet helps you managing your PERC using the LSI MegaCli command line tool. It isn't exhaustive but should be sufficient in most cases.
Also includes a quick walkthrough on how to change or replace a drive, if you're in a hurry... ;-)
There are a couple of PERC 5/i Nagios plugins out there in the wild but only two of them are really worth a look:
At rapidsoft we're using our own monitoring tool for which I've written a plugin for the PERC5/i.
The monitoring tool itself is (not yet) freeware, so you won't be able to use the plugin as it is – but you're welcome to use the code in your own checking/monitoring facility or build another Nagios plugin ;-).
This plugin directly uses the MegaCli tool (like check_megaraid_sas for Nagios) but it's a bit more sophisticated.
Download rs_check_raid_perc5i.class.php or view the colored source code.