3.5 KiB
Fenris
Fenris observes an NVMe drive’s real-world use and translates that history into an understandable endurance outlook.
Language
Observation history: The persisted record of drive activity gathered while Fenris monitoring is enabled, retained across restarts and reboots. Avoid: Calibration data, temporary history
Observed usage habit: The pattern of active, idle, and powered-off hours represented by the observation history, with recent sustained behavior carrying more relevance than distant behavior. Avoid: Current usage, benchmark workload
Usage-adjusted theoretical lifespan: The theoretical time until the drive’s write endurance is exhausted if its observed usage habit continues; it is an endurance projection, not a predicted hardware-failure date. Avoid: Future life, actual lifespan, failure date
Projection confidence: The degree to which the observation history is sufficiently long, complete, and stable to support the usage-adjusted theoretical lifespan. Avoid: Accuracy percentage, certainty
Monitoring period: A span during which Fenris monitoring is enabled; powered-off time remains part of the usage habit, while deliberately disabled time does not. Avoid: Daemon uptime, calibration window
Observation store:
The single SQLite database at /var/lib/fenris/observations.db that persists the observation history, monitoring periods, hour observations, day aggregates, and endurance baseline.
Avoid: Data directory, history.jsonl, the database (generic)
Hour observation: One row per UTC hour in the observation store, recording that hour's usage-habit split into active, idle, powered-off, and unknown seconds, plus write/read deltas, thermal evidence, and coverage. Avoid: Hourly record, hourly.jsonl entry
Day aggregate: One row per UTC day derived from hour observations; the grain at which usage-habit evidence is judged. Avoid: Daily summary, daily stats
Controller segment: A span of observation history within which the drive's controller identity is unchanged and counters are monotonic; write deltas are never computed across a segment boundary. Avoid: Counter reset handling, drive swap detection
Endurance baseline: The write-endurance value a projection consumes: a verified rated-TBW override stored with provenance when one exists, otherwise a coarse implied baseline derived from vendor wear and labeled as such. Avoid: TBW value, failure threshold, max writes
Sustained regime: The most recent stretch of the observation history over which the observed usage habit has been stable; the interval whose write rate the usage-adjusted theoretical lifespan consumes. Avoid: Current window, detection period
Habit change: A sustained divergence between recent and earlier daily write rates that starts a new sustained regime. Avoid: Spike, anomaly
Scenario range: The spread of lifespan projections computed from the 7-, 28-, and 90-day horizons of the observation history, shown in place of a statistical interval. Avoid: Confidence interval, error bar
Coverage: The share of wall-clock seconds inside monitoring periods whose usage-habit classification is known rather than unknown. Avoid: Uptime, sample count
Collection run: One scheduled or on-demand execution of the collector that interrogates the drive and extends the observation history. Avoid: Poll, daemon tick
Deliberate disable: A monitoring pause made through Fenris's own control path, closing the monitoring period so the paused time is excluded from the usage habit. Avoid: Manual stop, service stop