ZFS Pool Capacity Critical Alert - Troubleshooting Guide

KB 715377 - ZFS Pool Capacity Critical Alert - Troubleshooting Guide

Purpose

This document provides a standardized approach for handling and troubleshooting the ZFS Pool Capacity Critical alert, enabling rapid response to prevent storage exhaustion, performance degradation, and potential service outages.

Alert Name

ZFS Pool Capacity Critical

Alert Description

This alert is triggered when ZFS pool utilization exceeds 95%, indicating that the storage pool is critically full.

At this level, the system may experience:
  1. Severe performance degradation
  2. Increased write latency
  3. Risk of write failures
This condition significantly increases the risk of:
  1. Pool instability
  2. Application/service disruption
  3. Potential data loss scenarios

Severity

P1- Critical Impact

Possible Causes

  1. Rapid data growth or unexpected spikes
  2. Accumulation of snapshots
  3. Lack of storage cleanup
  4. Inefficient dataset usage
  5. No capacity planning or monitoring
  6. High fragmentation impacting usable space

L1 Engineer Actions

Step 1 – Log the Alert

  1. Log in to the monitoring system
  2. Review alert summary and affected pool

Step 2 – Create Ticket

  1. Immediately inform L2 team (P1 priority)
  2. Create an internal ticket including:
    1. Alert name
    2. Hostname
    3. Pool name
    4. Current utilization (%)
    5. Timestamp

Step 3 – Escalation (If required)

  1. Ensure immediate escalation to L2
  2. Share all relevant details

Step 4 – Documentation

  1. Update Issue Master Sheet with incident details
  2. Ensure tracking for critical incident

L2 Engineer Actions

Step 1 – Check Pool Status & Usage

zpool list
zpool status
  1. Verify pool capacity and health
  2. Identify utilization percentage

Step 2 – Analyze Fragmentation

zpool list
  1. Check fragmentation levels
  2. Identify performance impact

Step 3 – Immediate Mitigation

  1. Perform urgent cleanup:
    1. Remove unnecessary data
    2. Delete unused snapshots
  2. If cleanup is insufficient:
    1. Plan for pool expansion

Step 4 – OEM Escalation

  1. Inform OEM/vendor for:
    1. Capacity expansion
    2. Storage planning support

Step 5 – Capacity Expansion (If required)

  1. Add new disks or extend pool
  2. Monitor pool after expansion

Resolution

The issue is considered resolved when:
  1. ZFS pool utilization drops below critical threshold
  2. Sufficient free space is available
  3. No performance degradation observed
  4. Alert is cleared

Escalation

  1. L1 → L2: Immediate escalation for P1 alert
  2. L2 → OEM/Vendor: For storage expansion or hardware support

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