# Sensors ## Chapter 7.3: Monitoring Hardware Sensors Your toolkit for precise, in-depth hardware health diagnostics. > ℹ️ **Hardware Sensor Monitoring** > > * **Available to**: All user roles > * **Scope:** Individual node level > * **Permissions**: Read-only for all users > * **Data Source:** Real-time readings from BMC sensors via Redfish protocol ## Overview The **`Sensors`** **tab** is your tool for detailed hardware diagnostics. While the Summary tab's graphs help you spot trends over time, this page provides the exact, real-time numerical values and the official manufacturer-defined operating thresholds for every sensor in the node. This is the difference between seeing a fever chart and reading the exact temperature on a digital thermometer. All data here is polled directly from the Baseboard Management Controller (BMC), making it completely independent of the operating system. Use this read-only page to answer one critical question: "Is this component currently operating within its safe, predefined limits?" {% hint style="warning" %} **Always Get the Latest Data** The sensor data is a snapshot from when the page was loaded. To get the most up-to-the-minute readings from the node's BMC, remember to perform a **manual browser refresh (F5)**. {% endhint %} ## How to Triage a Sensor's Health The tables on this page are designed for quick and accurate assessment. To interpret any sensor reading, follow this three-step process. ### Three-Step Health Assessment Process 1. **Check the Status:** Look at the color-coded dot first for an immediate health summary. 2. **Read the Current Value**: See the real-time measurement being reported by the component. 3. **Compare with Thresholds**: Verify where the current value falls within the hardware's official safe operating range. #### Sensor Table Column Reference
ColumnDescription & Why It MattersHow to Use
StatusYour At-a-Glance Health Indicator: Good is normal. Warning or Critical means the sensor has crossed a predefined threshold and requires immediate attention.First check - prioritize non-green statuses
Current ValueThe Real-Time Reading: The precise, real-time measurement from the sensor (e.g., Volts, RPM, °C).Exact measurement - compare against expected ranges
ThresholdsThe Official Safe Operating Limits: These read-only values are defined by the hardware manufacturer. A Current Value outside these boundaries triggers a Status change.Reference ranges - understand normal vs. abnormal
{% hint style="warning" %} **Diagnostic Priority:** Always start with **Critical** status sensors, then **Warning**, then verify **Good** sensors for baseline understanding. {% endhint %} ## Sensor Category Deep Dive Each category of sensors provides insight into a different aspect of the node's physical health. ### Discrete Sensors These sensors act as simple binary (on/off, true/false) indicators for various system states. They are excellent for quick, definitive checks. #### **Common Examples:** * **Chassis Intrusion:** Detects if the case has been opened * **PSU Redundancy:** Confirms if the redundant power supply is healthy * **System Status:** Overall system health indicators 🖼️ $$Image: The Discrete Sensor table, showing examples like PSU Redundancy and Chassis Intrusion status.$$
#### **Interpretation Guide:** * **Good/OK**: Component functioning normally * **Warning**: Attention required but not critical * **Critical**: Immediate action required ### Voltage Sensors Think of these as the "heartbeat" and "blood pressure" monitor for the node's power system. They ensure that stable and correct voltages are being delivered to sensitive components. #### How to Interpret: * **Normal Behavior:** Current Value should be extremely stable. * **Warning Signs:** Significant fluctuations or drifts into Warning range. * **Potential Issues:** Early indicator of failing Power Supply Unit (PSU) or motherboard issue. 🖼️ $$Image: The Voltage sensor table, highlighting the Current Value in relation to the warning and critical thresholds.$$
#### **Critical Voltage Rails to Monitor:** * **12V Rails:** Primary power distribution * **5V Rails:** Legacy component power * **3.3V Rails**: Logic and memory power ### Fan Sensors These sensors are the "respiratory check" for the node's cooling system, reporting the speed (RPM) of each fan.
#### How to Interpret: A fan's status is determined by comparing its Current Value (RPM) against its predefined Thresholds. * **Good:** The fan is spinning within its normal, expected RPM range. * **Warning:** The fan's speed is too slow (impending failure) or too fast (high heat load), crossing a Warning threshold. This requires investigation. * **Critical:** The fan's speed has crossed a Critical threshold. This could mean it is spinning dangerously slow, dangerously fast, or has stopped entirely (0 RPM). This state requires immediate attention. {% hint style="success" %} **Fan Monitoring Best Practices:** * **Redundancy Check:** Verify multiple fans are operational. * **RPM Consistency**: Compare similar fans for consistent speeds. * **Trend Analysis:** Monitor for gradual RPM degradation. {% endhint %} ### Temperature Sensors This is the **"fever check**" for your node, providing precise temperature readings from critical components. This is your primary tool for identifying and preventing overheating. #### How to Interpret: * **Normal Operation**: Temperatures within manufacturer specifications. * **High Load:** Elevated but within acceptable ranges during heavy workloads. * **Cooling Issues**: Sustained high temperatures indicating cooling system problems. 🖼️ $$Image: The Temperature sensor table, with the °C/°F toggle visible.$$
#### Temperature Monitoring Zones: * **CPU Zones**: Processor thermal management * **Memory Zones**: DIMM thermal monitoring * **Ambient Zones**: Overall chassis temperature * **PSU Zones**: Power Supply Unit thermal monitoring {% hint style="warning" %} **Unit Toggle:** You can switch the display between Celsius (°C) and Fahrenheit (°F) using the toggle in the top-right corner of the table. {% endhint %} ## From Sensor Alert to Actionable Insight This page is your starting point for diagnosis. When you find a sensor with a non-good status, the goal is to turn that alert into actionable information for maintenance or support. ### Your Diagnostic Workflow ``` Sensor Alert → Event Correlation → Evidence Gathering → Action Planning ``` **Step-by-Step Process:** 1. **Identify the Fault:** Note the full name of the sensor reporting an issue (e.g., "CPU1 DIMM A2 Temperature"). 2. **Find the Correlating Event**: Immediately navigate to the BMC SEL tab. The system automatically logs a detailed event that corresponds directly to the sensor alert. 3. **Gather the Evidence**: The event log provides the precise timestamp and error details. 4. **Take Action:** This collected evidence is exactly what you need to provide to a technician for a physical inspection or to a vendor for technical support. ### Documentation Template for Support When escalating sensor issues, include: * **Node Identity**: System Name and Serial Number * **Sensor Details**: Full sensor name and current reading * **Threshold Information**: Operating limits and current status * **Event Log Entry**: Corresponding BMC SEL event with timestamp * **Environmental Context**: Workload and environmental conditions ## Sensor Monitoring Best Practices ### Daily Health Check Routine 1. **Priority Scanning**: Check for any Critical or Warning status indicators. 2. **Baseline Verification:** Note normal operating ranges for your environment. 3. **Trend Correlation**: Compare with Summary tab trends for context. 4. **Event Correlation**: Cross-reference with BMC SEL for related events. ### Proactive Monitoring Strategies #### Establish Baselines: * Document normal operating ranges for each sensor type. * Note typical values during different workload conditions. * Track seasonal variations in temperature readings. #### Early Warning Detection: * Monitor sensors approaching warning thresholds. * Track gradual changes that might indicate developing issues. * Correlate sensor patterns across similar nodes. ### Integration with Other Monitoring #### Cross-Reference Points: * **Summary Tab:** Use graphs for trend analysis. * **BMC SEL:** Check for corresponding system events. * **Operations Tab**: Verify system operations impact on sensors. * **Services Tab**: Correlate with service health status. ## Chapter Summary & Key Takeaways * **Summary is for Trends, Sensors is for Thresholds**: Use the Summary tab to see graphs over time. Use this Sensors tab to see the exact current value and compare it against the official safe operating limits. * **Refresh is Required**: The data is a snapshot. Always manually refresh (F5) to get the latest readings. * **Your Goal is Evidence**: A sensor alert is your clue. The detailed event in the BMC SEL tab is your evidence for taking action. * **Follow the Workflow**: Sensor Alert → Event Correlation → Evidence Gathering → Support Action. * **Monitor Proactively**: Establish baselines and track trends to prevent issues before they become critical. #### What's Next: Chapter 7.4 will explore the BMC System Event Log (SEL), where you'll learn to investigate the detailed hardware events that correspond to sensor alerts and system activities. > 💡 **Pro Tip**: Create a baseline document of normal sensor readings for each node type in your environment - this makes identifying abnormal conditions much faster and more accurate.