A RAID controller keeps an array online when one disk fails, but that protection ends the moment a second drive goes or the controller itself reports a problem. Nagios XI polls the controller for its own status and alerts the moment an array, a physical disk, or the battery-backed cache leaves a healthy state, so a Degraded array doesn’t sit unnoticed until an application starts throwing errors.

A RAID controller is the hardware or firmware layer that groups physical disks into a redundant array and presents them to the operating system as a single logical drive. RAID controller monitoring polls that controller for the state it already tracks, the array’s status (Optimal, Degraded, or Failed), the status of each physical disk, and the health of any battery-backed write cache, and turns a change in that state into an alert.

RAID data loss almost always follows the same pattern: one drive fails, nobody notices the array is Degraded, and a second drive fails before the first is replaced.

• Catch a degraded array before the second drive fails: An alert the moment the array leaves Optimal gives you a window to replace the failed disk while the array still has redundancy.
• See rebuild progress: Know when a rebuild is running so a performance dip is explained rather than troubleshot as unrelated.
• Track battery-backed cache health: A disabled write cache can quietly slow every write to the array.
• Keep storage issues in the same view as everything else: RAID status sits next to your other storage monitoring checks instead of requiring a separate login to the controller’s own utility.

Nagios XI doesn’t ship a RAID controller plugin by default. RAID status comes from a community plugin, available on Nagios Exchange, that calls your controller’s own vendor tool (such as StorCLI, MegaCli, ssacli, or arcconf) or an SNMP agent. Once uploaded into Nagios XI, it reports:

• Array status: Optimal, Degraded, Failed, or Rebuilding, as a Nagios Service.
• Physical disk status: A failed, missing, or predictive-failure disk within the array.
• Battery-backed write cache health: Whether the cache is enabled and whether the battery is mid learning-cycle.
• Custom thresholds: A different Nagios state for each condition, for example Warning during a resync and Critical for a degraded array.

Documentation: RAID Controllers on Nagios Exchange | How To Use The Generic Plugin Wizard In Nagios XI

Fewer surprise data-loss incidents: A second drive failing in a Degraded array is how most RAID data loss happens. An alert the moment the array leaves Optimal gives you the window to replace the failed drive first.

Faster root-cause on storage-related slowdowns: When application latency traces back to a rebuilding array or a disabled write cache, that state shows up alongside the host’s other checks.

One alerting path for the whole controller fleet: Array status, physical disk state, and battery health for every RAID controller reach the same interface, notification rules, and on-call escalation as the rest of your infrastructure checks.

Nagios XI reports the array and disk state the RAID controller already tracks, and turns a change in that state into an alert. It doesn’t replace the controller’s own management utility for creating or repairing an array, and it doesn’t forecast which drive fails next; it reports what the controller reports.

• Storage Monitoring
• S.M.A.R.T. (SMART) Monitoring
• Disk Monitoring
• Server Monitoring
• NAS & SAN Monitoring