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SD Card Exporter Documentation

This exporter monitors the health and performance of an SD card using B&R X20 Edge tools and exposes the data in Prometheus-compatible format.

It builds upon the B&R use case documented at:
SD Card Health

📝 Overview​

The sdcard-exporter is a containerized Python application that uses:

  • mmc utility (from B&R) to retrieve SMART data from /dev/mmcblk1
  • iostat to gather disk usage statistics
  • prometheus_client Python module to expose metrics on port 8000

These metrics are scraped by Prometheus and visualized in Grafana.

🐳 Container Structure​

Folder structure:

Monitoring/
├── docker-compose.yml
├── prometheus/
│   ├── prometheus.yml
│   └── _data/              # Prometheus data volume
└── SdcardHealth/
    ├── Dockerfile
    ├── sdcard-exporter.json    # Grafana dashboard export
    └── app/
        ├── exporter.py         # Python exporter script
        └── mmc                 # MMC binary from B&R

📊 Exported Metrics​

From mmc smart /dev/mmcblk1​

  • sd_card_health_percent
  • sd_card_bad_blocks
  • sd_card_spare_blocks
  • sd_card_min_erase_count
  • sd_card_max_erase_count
  • sd_card_total_erase_count
  • sd_card_avg_erase_count
  • sd_card_pe_cycles
  • sd_card_power_cycles
  • sd_card_write_crc_errors

From iostat -d -o JSON​

  • iostat_util_percent
  • iostat_tps
  • iostat_kb_read_s
  • iostat_kb_wrtn_s
  • iostat_kb_read
  • iostat_kb_wrtn

🚀 Running the Exporter​

The container is built and managed via Docker Compose. Here's a snippet from docker-compose.yml:

  sdcard-exporter:
    build: ./SdcardHealth
    container_name: sdcard-exporter
    restart: unless-stopped
    privileged: true
    cap_add:
      - SYS_RAWIO
      - SYS_ADMIN
    devices:
      - "/dev/mmcblk1:/dev/mmcblk1"
    volumes:
      - "/dev:/dev"
    expose:
      - "8000"
    user: "0:0"
    tty: true
    stdin_open: true
    networks:
      - monitoring

📡 Prometheus Integration​

Add this job to prometheus/prometheus.yml:

  - job_name: 'sdcard-exporter'
    static_configs:
      - targets: ['sdcard-exporter:8000']

📊 Grafana Dashboard​

Import the dashboard:

Go to Grafana → Dashboards → Import

Upload sdcard-exporter.json from the SDcardHealth folder

Set Prometheus as the data source

Alternatively, you can customize this dashboard using B&R’s original templates or your own metrics.

⚙️ Notes​

The exporter must run with root privileges (user: "0:0", privileged: true) to access SD card diagnostics.

Make sure /dev/mmcblk1 matches your system's SD card device.

The Python script sleeps 15 seconds between metric reads. Adjust this if needed.

For visual examples and step-by-step dashboard import, refer to the main documentation file: monitoring-stack.md.