Complete rewrite: SnapRAID SMART logger with BackBlaze algorithm

Fetches SMART data from Scrutiny's InfluxDB and calculates failure
probabilities using the exact BackBlaze tables from SnapRAID source.

Key features:
- Calculates both v12 (with attr 193) and v13 (without attr 193) algorithms
- v12 matches SnapRAID pre-v13.0 (includes Load Cycle Count)
- v13 matches modern SnapRAID v13.0+ (excludes Load Cycle Count)
- Stores both values for trending and comparison
- Correctly applies bit masks (16-bit for 187/188, 32-bit for others)
- Annualizes monthly rates and applies Poisson distribution
- Logs to PostgreSQL with device metadata

Solved the mystery: SnapRAID v12 uses attribute 193 which was removed
in v13.0. Load cycle count has massive impact on failure predictions
for some drives (80% vs 4% difference).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

get_device_info.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""
+Helper script to extract WWN to device mappings from InfluxDB.
+Run this to help populate the devices table.
+"""
+
+import os
+from influxdb_client import InfluxDBClient
+from dotenv import load_dotenv
+
+load_dotenv()
+
+def get_device_info():
+    """Extract unique device WWNs and their latest data from InfluxDB."""
+    url = os.getenv('INFLUXDB_URL')
+    token = os.getenv('INFLUXDB_TOKEN')
+    org = os.getenv('INFLUXDB_ORG', 'scrutiny')
+    bucket = os.getenv('INFLUXDB_BUCKET', 'metrics')
+
+    print(f"Connecting to InfluxDB at {url}...")
+    client = InfluxDBClient(url=url, token=token, org=org)
+    query_api = client.query_api()
+
+    # Get unique device WWNs with their latest data
+    query = f'''
+    from(bucket: "{bucket}")
+        |> range(start: -24h)
+        |> filter(fn: (r) => r._measurement == "smart")
+        |> filter(fn: (r) =>
+            r._field == "temp" or
+            r._field == "power_on_hours"
+        )
+        |> last()
+        |> group(columns: ["device_wwn", "device_protocol"])
+    '''
+
+    print("\nDiscovered devices:\n")
+    print("=" * 80)
+
+    result = query_api.query(query)
+    devices = {}
+
+    for table in result:
+        for record in table.records:
+            wwn = record.values.get('device_wwn')
+            protocol = record.values.get('device_protocol')
+
+            if wwn not in devices:
+                devices[wwn] = {
+                    'wwn': wwn,
+                    'protocol': protocol,
+                    'temp': None,
+                    'power_on_hours': None
+                }
+
+            field = record.get_field()
+            if field == 'temp':
+                devices[wwn]['temp'] = record.get_value()
+            elif field == 'power_on_hours':
+                devices[wwn]['power_on_hours'] = record.get_value()
+
+    # Print devices
+    for i, (wwn, info) in enumerate(sorted(devices.items()), 1):
+        power_on_days = int(info['power_on_hours']) // 24 if info['power_on_hours'] else 0
+
+        print(f"Device {i}:")
+        print(f"  WWN: {wwn}")
+        print(f"  Protocol: {info['protocol']}")
+        print(f"  Temperature: {info['temp']}°C")
+        print(f"  Power-On Time: {power_on_days} days ({info['power_on_hours']} hours)")
+        print()
+
+    print("=" * 80)
+    print("\nNow run 'snapraid smart' or 'smartctl -a /dev/sdX' on each device to get:")
+    print("  - Serial number")
+    print("  - Model name")
+    print("  - Capacity")
+    print("  - Device path (/dev/sdX)")
+    print("\nThen update populate_devices.sql with this information.")
+
+    client.close()
+
+
+if __name__ == '__main__':
+    if not os.getenv('INFLUXDB_URL'):
+        print("ERROR: Please create a .env file with your InfluxDB configuration")
+        exit(1)
+
+    get_device_info()