86 lines
4.6 KiB
Markdown
86 lines
4.6 KiB
Markdown
# Fenris
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Fenris observes an NVMe drive’s real-world use and translates that history into an understandable endurance outlook.
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## Language
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**Observation history**:
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The persisted record of drive activity gathered while Fenris monitoring is enabled, retained across restarts and reboots.
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_Avoid_: Calibration data, temporary history
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**Observed usage habit**:
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The pattern of active, idle, and powered-off hours represented by the observation history, with recent sustained behavior carrying more relevance than distant behavior.
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_Avoid_: Current usage, benchmark workload
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**Usage-adjusted theoretical lifespan**:
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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.
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_Avoid_: Future life, actual lifespan, failure date
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**Projection confidence**:
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The degree to which the observation history is sufficiently long, complete, and stable to support the usage-adjusted theoretical lifespan.
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_Avoid_: Accuracy percentage, certainty
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**Monitoring period**:
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A span during which Fenris monitoring is enabled; powered-off time remains part of the usage habit, while deliberately disabled time does not.
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_Avoid_: Daemon uptime, calibration window
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**Observation store**:
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The single SQLite database at `/var/lib/fenris/observations.db` that persists the observation history, monitoring periods, hour observations, day aggregates, and endurance baseline.
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_Avoid_: Data directory, history.jsonl, the database (generic)
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**Store fault**:
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The condition where the observation store is present but cannot be read or trusted — unreadable, corrupt, or written by a newer Fenris — degrading every view that depends on it rather than crashing or guessing.
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_Avoid_: Database error, corruption, broken data
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**Hour observation**:
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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.
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_Avoid_: Hourly record, hourly.jsonl entry
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**Day aggregate**:
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One row per UTC day derived from hour observations; the grain at which usage-habit evidence is judged.
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_Avoid_: Daily summary, daily stats
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**Controller segment**:
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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.
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_Avoid_: Counter reset handling, drive swap detection
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**Degraded identity**:
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The condition where a controller segment's identity key is blank because no identifier rung produced a value; replacement detection then relies on write-counter continuity alone, and projection confidence is capped.
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_Avoid_: Identity error, unknown device, virtual drive
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**Endurance baseline**:
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The write-endurance value a projection consumes, chosen by precedence: a verified override when one exists, otherwise an unverified override, otherwise a coarse implied baseline derived from vendor wear — each labeled as such.
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_Avoid_: TBW value, failure threshold, max writes
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**Verified override**:
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A rated-TBW override with complete provenance whose applicability to the detected drive was confirmed by machine match or explicit user attestation; the strongest endurance baseline.
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_Avoid_: Confirmed TBW, trusted value
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**Unverified override**:
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A rated-TBW override knowingly stored with incomplete provenance; always presented as user-supplied, never as verified.
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_Avoid_: Forced entry, fallback baseline
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**Sustained regime**:
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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.
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_Avoid_: Current window, detection period
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**Habit change**:
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A sustained divergence between recent and earlier daily write rates that starts a new sustained regime.
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_Avoid_: Spike, anomaly
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**Scenario range**:
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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.
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_Avoid_: Confidence interval, error bar
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**Coverage**:
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The share of wall-clock seconds inside monitoring periods whose usage-habit classification is known rather than unknown.
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_Avoid_: Uptime, sample count
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**Collection run**:
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One scheduled or on-demand execution of the collector that interrogates the drive and extends the observation history.
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_Avoid_: Poll, daemon tick
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**Deliberate disable**:
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A monitoring pause made through Fenris's own control path, closing the monitoring period so the paused time is excluded from the usage habit.
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_Avoid_: Manual stop, service stop
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