Research storage measurements and health evidence

docs/research/speedometer-offline-pack.md

@@ -1,33 +0,0 @@
-# Speedometer 3.1 offline pack at the pinned upstream commit
-
-## Decision-ready finding
-
-The pinned [WebKit/Speedometer commit `1386415be8fef2f6b6bbdbe1828872471c5d802a`](https://github.com/WebKit/Speedometer/commit/1386415be8fef2f6b6bbdbe1828872471c5d802a) is a plausible source for an Odin **versioned browser workload** served from localhost. It contains built static applications and the benchmark runner. Its page identifies itself as Speedometer **3.1**, although `package.json` still says `3.0.0-alpha`; identify the pack by the full commit and a content digest, not that package version. The [about page](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/about.html) says workloads are built as static files and cannot depend on server infrastructure. The [runner](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/benchmark-runner.mjs) loads each suite in an iframe under `resources/`.
-
-This is a **conditional yes** for an offline pack. Source inspection and static link checks support completeness, but they do not prove that a browser makes no external requests or that every workload succeeds without internet. Require a blocked-network browser smoke test before calling the pack offline-ready. This research did not execute a benchmark or install a browser.
-
-## Pack contents and static checks
-
-The [suite list](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/tests.mjs) declares 32 suites, 20 enabled by default. Local inspection of the pinned source archive found every declared suite entry path. The archive contained 1,118 files totaling 61,022,359 uncompressed bytes. For the root page plus the 20 enabled suite entry pages, a static HTML parser checked 194 `script`, asset `link`, and `img` references: none was external or missing. These numbers describe the checked archive, not a run result. The parser did not resolve dynamic JavaScript imports, CSS URLs, route requests, or user navigation.
-
-The [main page](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/index.html) loads local CSS and `resources/main.mjs`; the [runner](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/benchmark-runner.mjs) constructs `resources/${suite.url}`. The Perf Dashboard workload deserves special attention: its [static page](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/perf.webkit.org/public/v3/index.html) replaces its API method with `mockAPIs()` and fetches 13 specified local JSON paths. All 13 files exist in the pinned archive. The ordinary [dashboard remote API](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/perf.webkit.org/public/v3/remote.js) supports XHR, so verify the mock remains active in the actual packaged page.
-
-No `npm install` is needed to serve the already built workload assets. Upstream [development instructions](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/Development.md) use `http-server` for local development. Odin can serve the frozen file tree with its own loopback-only static server; do not rebuild application assets as part of a benchmark run. Use an HTTP origin rather than `file://`, since the suite uses modules, iframe paths, and fetches. The [upstream test harness](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/tests/run.mjs) is Selenium based and requires an installed browser and matching driver, per [Testing.md](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/Testing.md); it is not a prerequisite for serving the built pack.
-
-## Redistribution boundary
-
-The root [LICENSE](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/LICENSE) permits source and binary redistribution with or without changes if its copyright notice, conditions, and disclaimer are retained or reproduced as specified. This is not a blanket license for all included third-party work. The [TodoMVC subtree license](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/todomvc/license.md) states MIT unless otherwise specified and requires inclusion of its notice in copies or substantial portions. Built bundles also carry license files, including [React bundle notices](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/todomvc/architecture-examples/react/dist/app.bundle.js.LICENSE.txt), [Angular third-party notices](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/todomvc/architecture-examples/angular/dist/3rdpartylicenses.txt), and [React Stockcharts notices](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/react-stockcharts/build/static/js/2.8e539c84.chunk.js.LICENSE.txt).
-
-Pack the complete upstream notice files alongside their assets, preserve inline notices, and record a notice inventory with the pack manifest. A complete third-party license audit remains unresolved: the archive includes many generated bundles and assets, and finding a root license plus named notice files does not establish licensing for every individual asset. Review the final redistributed file set and notices before shipping. This is a licensing assessment from primary source text, not legal advice.
-
-## Browser mode and result identity
-
-Upstream [test instructions](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/instructions.html) call for a latest stable browser, clean profile, focused page, closed competing tabs, and no interaction during the run. The [page](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/index.html) warns when its visible viewport is below 850 × 650. The [parameters](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/params.mjs) separately default the suite iframe to 800 × 600 and expose iteration count, suite selection, and timing method. Record these exact conditions in Odin's run record.
-
-Use a headed, focused browser session for the comparable browser workload. Upstream provides no headless equivalence claim in the cited instructions or [Selenium runner](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/tests/run.mjs). Headless may be useful for a smoke test, but treat any headless measurement as a distinct software mode until equivalence is demonstrated. Do not silently mix browser versions, profiles, window/iframe sizes, suite selections, or headed/headless results in one calibrated measurement.
-
-## Manifest and offline acceptance proposal
-
-Create a deterministic, content-addressed pack manifest. Record: upstream repository URL and full commit; Speedometer 3.1 display version; every shipped relative path with byte length and SHA-256; a sorted inventory of license/notice paths; default suite names; and packaging schema version. Hash canonical serialized manifest bytes for the pack identifier. Verify each file hash before serving; reject missing, extra, or changed files. Keep the complete source snapshot or an auditable mapping from snapshot to shipped subset. This is an Odin design recommendation based on the pinned [runner paths](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/benchmark-runner.mjs), [suite list](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/resources/tests.mjs), and [license](https://github.com/WebKit/Speedometer/blob/1386415be8fef2f6b6bbdbe1828872471c5d802a/LICENSE); upstream does not prescribe this manifest.
-
-Before a benchmark run, validate offline behavior without collecting a score: serve the frozen tree on loopback, open the landing page and each default suite page in a disposable browser profile, disable outside network at the browser or sandbox boundary, log attempted requests, and check that all required assets load with no external request or console error. Include dynamic imports, CSS fonts/images, redirects, worker requests, and the Perf Dashboard JSON paths. Do not click Start Test during this gate. If the gate fails, report the missing/remote URL and mark the browser workload unavailable; do not substitute an online fetch. This acceptance procedure is proposed, not claimed as completed.

docs/research/storage-health.md

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+# Storage measurements and trustworthy health advice
+
+Research for [Establish storage measurements and trustworthy health advice](https://git.bongbetic.com/xavierk/odin/issues/4), part of Odin's Wayfinder map. Access date for every source: **2026-09-25**.
+
+This report establishes evidence and candidate policies. It does not select Odin's final workloads, thresholds, privileged execution design, or score. No benchmark, device query, self-test, installation, or hardware change was performed during this investigation.
+
+## Findings that shape the decision
+
+The strongest candidate is **fio for file-based performance measurements, smartmontools for cross-protocol health findings, and an optional nvme-cli adapter for additional NVMe evidence**. These tools cover different responsibilities. A fast benchmark cannot establish drive health; a passing SMART status cannot establish future reliability. Health findings should therefore remain visible independently of the performance score and capability coverage.
+
+There is a material compatibility change already: nvme-cli **v3.1**, released September 18, 2026, documents `nvme log smart`; `nvme smart-log` is a deprecated compatibility alias. Its default output format version is now 2, with version 1 available. fio **3.43** was released September 23. A bleeding-edge development environment is compatible with reproducible measurements only if Odin records tool versions and keeps workload and parser versions explicit. Package-manager availability alone does not establish supported commands or JSON schemas. [S1][S3]
+
+## Candidate tools and measurement scope
+
+| Candidate | Useful responsibility | Limits and recommendation to consider |
+| --- | --- | --- |
+| fio | Sequential/random reads and writes, block sizes, queue depths, latency distributions, bounded I/O, optional verification | Best primary workload candidate. Select a small fixed workload vocabulary; do not accept arbitrary user-supplied job files into privileged execution. |
+| smartctl | ATA, SCSI and NVMe identity, health, existing error/self-test logs; JSON; many bridge/controller adapters | Best baseline health reader. Decode protocol-specific semantics and command status separately. Some transports are unsafe for automatic probing. |
+| nvme-cli | NVMe-specific identity, SMART and detailed logs | Useful optional supplement. Version 2/3 command and JSON differences need explicit compatibility handling. Avoid duplicating the same controller's health as several independent findings. |
+| Native `/proc` and `/sys` | I/O pressure, completed I/O, queue activity and available sensors | Low-dependency contextual evidence, not a workload or a substitute for SMART. |
+| GNU `dd` | Bounded sequential copying, optionally direct I/O and final synchronization | Possible explicitly labelled basic fallback. Its copy-oriented output does not supply fio's workload control or latency distributions; its result must not silently substitute into the same scored workload. |
+
+Sources: fio HOWTO, smartctl manual, nvme-cli released documentation, kernel PSI/I/O documentation and GNU manual. [S1–S4][S8][S9][S14]
+
+A compact candidate performance set is:
+
+| Measurement | Candidate workload, still to be selected | What its result means |
+| --- | --- | --- |
+| Sequential read/write | Large blocks, for example 1 MiB, one job, depth 1 | Large-file throughput through the selected filesystem and storage path |
+| Random read/write | 4 KiB, one job, depth 1 | Small-request responsiveness; report latency and IOPS |
+| Queued random read | Same block size at a documented higher depth, such as 16 or 32 | Concurrency capability; a different workload from depth 1 |
+| Durable small writes | A separate small, bounded workload with defined sync frequency | Application-visible cost of requesting persistence |
+| Optional integrity check | Write and verify Odin-owned file blocks with fio checksums | Whether the tested data path returned those bytes correctly; not a full-surface drive or whole-RAM certification |
+
+Record read and write throughput in explicit units, IOPS, completed bytes, operation count, errors, elapsed time, and p50/p95/p99 latency where sample counts support them. Distinguish fio completion latency from total latency: total includes submission latency. Record achieved queue-depth distribution; requesting depth greater than one does not make a synchronous engine asynchronous. fio `psync` is a useful depth-1 compatibility candidate; `io_uring` and `libaio` are queued-engine candidates where supported. Engine changes must be visible in results and comparability rules. [S1]
+
+Measure one storage workload at a time during reference runs. Concurrent CPU or memory stress can instead be an explicitly identified contention experiment. Record filesystem, mount options, device topology, encryption/RAID/virtualization, kernel, selected engine, power/thermal state, background I/O, and pre/post free space. The measurement describes this path under these conditions, not the NVMe/HDD in isolation.
+
+## Safe operation and comparability constraints
+
+The following are proposed invariants, rather than finalized profile numbers:
+
+1. **Own every writable byte.** Create a private run directory on a deliberately selected filesystem and exclusively create its regular files. Validate ownership, type and target identity; reject symlink redirection and raw block/character devices. `O_CREAT|O_EXCL` supplies exclusive creation semantics. Do not use arbitrary existing user files as write targets. Avoid selecting `/tmp` automatically: tmpfs stores files in virtual memory and may use swap. [S7][S11]
+2. **Budget storage space and cumulative writes separately.** fio `size` defines the working region, while `io_size` can independently bound I/O. `runtime` stops at the earlier of completion or time limit; `time_based` loops the workload. Thus a small file plus a timed loop can write many times its size. Prefer explicit byte and time bounds without `time_based` for ordinary write profiles. Count fixture preparation, repetitions and verification-related writes in a per-run host-write budget. Reserve free space, account for quotas and metadata, recheck during execution, and stop on ENOSPC or I/O errors. Space and byte thresholds remain product decisions. [S1]
+3. **Do not promise a physical NAND-write limit.** A workload's host bytes are measurable; filesystem/controller write amplification and unrelated host activity are additional. NVMe Data Units Written measures host data in units of 1,000 × 512 bytes, rounded up, excluding metadata; it is not a universal NAND-wear counter. Background activity also prevents attributing its entire delta to Odin. [S5]
+4. **Make cache and durability modes explicit.** fio `direct=1` normally requests `O_DIRECT`; support and alignment vary by filesystem and kernel, and misaligned requests can fail or fall back to buffered I/O. Direct I/O does not by itself provide `O_SYNC` persistence guarantees, bypass every device cache, or prove sustained media speed. `invalidate` is conditional on platform/file support. Avoid global `drop_caches`: kernel documentation warns of additional I/O and CPU costs. A buffered fallback must be labelled and excluded from direct-I/O comparisons. [S1][S7][S12]
+5. **Include preparation and flush costs honestly.** Read tests over newly created fixtures still require writes. A user choosing no writes can reuse an identified valid fixture or skip that workload; Odin should not create one silently. Do not measure unwritten sparse-file holes as disk reads. For writes, document `end_fsync` or other synchronization and report end-to-end time including the final flush separately from unsynchronized throughput. Control data compressibility/deduplication using a declared fio buffer policy; generating fresh data adds CPU cost. Preserve normal filesystem settings rather than silently disabling compression or copy-on-write. [S1][S7]
+6. **Treat cancellation and cleanup as part of the run.** Bound the entire job group; stop launching work on cancellation, retain partial status, reap workers, and remove only proven Odin-owned artifacts. A worker stuck in kernel I/O may not stop immediately. Crash recovery needs a manifest and ownership checks before deletion. Cleanup failure is a reported outcome, never a reason to recursively delete a user-selected directory.
+7. **Collect health before load and reduce work when evidence is serious.** A candidate policy is to skip storage stress when critical media/reliability findings or current unreadable data are already present. Pause on documented thermal alarms or loss of safety headroom. Display estimated host writes before a write run. Avoid automatic discard/TRIM, formatting, SMART feature changes, firmware updates, cache-policy changes or repair operations as benchmark preparation.
+
+Short bounded tests cannot establish steady-state SSD performance after exhaustion of a large write cache, or scan every HDD sector. Making test data larger than all caches can conflict with a quick run and a conservative write budget. Report the actual duration and working set; do not extrapolate a short burst into an endurance or sustained-performance guarantee. The tradeoff between low impact and sustained measurements needs an explicit run-profile decision.
+
+## Health evidence and field interpretation
+
+Prefer structured output with the original tool version, schema identifier, command outcome, timestamp, device identity and transport. A missing field is unknown, not zero. Preserve large counters losslessly: smartctl JSON can emit string/byte-array companions for integers exceeding JavaScript's safe integer range; `--json=v` requests them consistently. This matters for an Ink/JavaScript consumer. [S2]
+
+For smartctl NVMe output, the primary object is `nvme_smart_health_information_log`. The inspected source confirms the following keys and conversions. Raw NVMe temperature is Kelvin; smartctl's `temperature` here is already Celsius. Do not convert it twice. [S6]
+
+| Evidence | Meaning | Candidate interpretation |
+| --- | --- | --- |
+| `critical_warning` bit 0; `available_spare` vs `available_spare_threshold` | Spare capacity below the controller's threshold | Urgent preservation/service finding; display the device-provided threshold |
+| Bit 1; `temperature`, warning/critical temperature time | Above an over-temperature or below an under-temperature threshold | Stop heat-producing tests; investigate cooling/environment. This alone is not proof that replacement is needed |
+| Bit 2 | NVM subsystem reliability degraded | Urgent backup and replacement/service assessment |
+| Bit 3 | Media placed read-only for a device reliability condition | Urgent preservation and replacement/service assessment; distinct from user namespace write protection |
+| Bits 4/5 | Volatile-memory backup failure; persistent-memory region read-only/unreliable | Urgent loss-of-protection/service finding when applicable; explain the specific subsystem |
+| `percentage_used` | Vendor estimate of endurance consumed | 100 means estimated endurance consumed, **not guaranteed failure**; values may exceed 100. Plan replacement according to manufacturer guidance and workload, without inventing days remaining |
+| `media_errors` | Unrecovered data-integrity errors, including ECC/CRC/tag errors | Investigate any nonzero history; escalating recent deltas plus failed I/O are much stronger urgent evidence than an isolated old count |
+| `num_err_log_entries` | Lifetime number of error-information entries | Inspect status/cause and recency. It is not interchangeable with media errors |
+| `unsafe_shutdowns` | Loss of power without shutdown notification | Investigate shutdown/power history and correlate with errors; not proof of failed media |
+| `data_units_written`, power-on hours, thermal counters | Usage/history with specified units and reporting limits | Useful trends and context; no universal lifespan formula |
+
+NVMe warning bits are current state, not persistent event history; zero today does not erase yesterday's finding. Some temperature fields are optional, and zero can mean unsupported. Per-namespace SMART is optional; the global namespace identifier can describe a controller's aggregate. Preserve scope rather than assigning identical controller totals to every namespace. [S3][S5][S6]
+
+**ATA needs a separate mapping.** Keep attribute ID, raw representation, normalized current/worst value, threshold, type and failure state. smartctl states that these meanings are vendor-specific; SSD meanings can differ and displayed names can be wrong for models absent from its drive database. The label `Pre-fail` by itself does not mean a drive is failing: the current normalized value must cross its threshold. [S2]
+
+Common drive-database candidates include reallocated sectors (5), pending sectors (197), offline uncorrectable sectors (198), and interface CRC errors (199). Interpret them only with a matching model/firmware/database rule; do not apply a universal raw-count threshold or turn interface errors directly into a disk-replacement recommendation. Preserve lifetime history and recent deltas separately. SMART RETURN STATUS, failed applicable thresholds, existing self-test failures, and observed host I/O errors are stronger when they agree. SCSI health uses its own exception/sense reporting rather than ATA attribute assumptions. [S2][S15]
+
+smartctl exit status is a bitmask. Bits 0–2 can describe invocation/access/command problems; bits 3–7 describe failing status, thresholds and historical error/self-test evidence. A nonzero exit must not discard usable JSON, and access failure must not become “bad drive.” Reading an existing self-test log is different from starting a test. The manual notes that running self-tests can degrade performance and normal I/O can extend their duration; any future self-test workflow needs a separate user decision and scheduling. [S2]
+
+## Candidate advice rubric
+
+This rubric is a proposed interpretation layer over the documented evidence, not a manufacturer's warranty or an adopted Odin policy.
+
+| Finding class | Evidence sufficient to consider it | Appropriate wording/action |
+| --- | --- | --- |
+| **Replace/service now** | Credible ATA failing status/current applicable prefailure threshold; NVMe degraded reliability/read-only media; serious repeated data-integrity failures attributable to the device | “Preserve accessible data now; avoid further stress; arrange replacement or service.” Cite exact flags, device scope and timestamps. Hardware attribution may still need confirmation |
+| **Investigate urgently** | New media errors, pending/uncorrectable sectors, recent failed self-tests, resets/timeouts, thermal alarms, loss of power-loss protection | Identify the failing path; correlate controller, connection, power and filesystem evidence. Do not automatically blame the medium |
+| **Monitor / plan replacement** | Stable historical findings or vendor-estimated endurance consumed without current failure evidence | Retain trends, explain wear status and manufacturer limits, and plan according to importance/workload. No invented remaining-life percentage |
+| **No concerning evidence observed** | Successful supported collection with no relevant current finding | State what was checked and when; keep normal backup advice independent of a performance score |
+| **Unknown / limited coverage** | Missing permission/tool/field, sleeping drive, unsupported bridge/controller, virtual device, ambiguous identity | Explain the missing capability and a bounded next step. Never convert unavailable evidence into a healthy badge |
+
+The smartctl manual recommends preserving data promptly when the drive reports failing health. Conversely, Google's primary HDD population study found that SMART-only models were unlikely to predict individual failures reliably. That older HDD result is not a calibrated modern-SSD failure model, but it reinforces the distinction between a useful warning and a guarantee of future health. NVMe's own endurance-field semantics explicitly reject equating 100% usage with failure. [S2][S5][S16]
+
+## Compatibility, privilege and general health
+
+USB, SAT and RAID support must follow known transport rules. The smartctl manual documents bridge-specific NVMe adapters and per-physical-disk MegaRAID addressing; a RAID logical volume is not automatically one physical drive. Particularly important: its **JMB39x/JMS56x transport uses READ/WRITE commands to a RAID-volume sector**. It warns that the wrong device can be overwritten and interruption can prevent restoration. Exclude these from routine automated probing; “try every device type” is not a safe compatibility strategy. Even standby-aware queries may wake a disk during autodetection, so record unsupported power-state handling. [S2]
+
+VMs need an explicit virtual-device classification. QEMU's NVMe implementation constructs SMART data from its emulated controller and block-accounting state. A guest can therefore show valid-looking SMART without revealing the host drive's health. Guest tests establish guest-path performance; actual physical passthrough and device identity require separate verification. VM coverage cannot establish USB, physical RAID, real wear counters or thermal behavior. [S17]
+
+Keep ordinary file workloads unprivileged. Device queries may require additional device permissions or kernel capabilities; NVMe's Linux passthrough code explicitly gates classes of commands. A future privileged mechanism should allow only validated read operations and selected devices, with no arbitrary shell or passthrough-command forwarding. Permission denial is an expected capability outcome, not an instruction to run the whole TUI as root. [S18]
+
+For overall system health, useful complementary evidence is:
+
+- `/proc/pressure/io`: `some` measures time with some stalled tasks, `full` time with all non-idle tasks stalled; use same-window deltas alongside workload latency. This detects pressure, not its sole cause. [S8]
+- `/proc/diskstats` or per-device sysfs statistics: completed I/O, time and queue context. Counters have concurrency/accounting caveats; busy percentage alone does not establish NVMe saturation. [S9]
+- Available hwmon readings, limits and alarm flags: retain sensor identity and units; chip-specific alarms and missing sensors preclude a universal hard-coded temperature cutoff. Standard hwmon ABI readings are intended to be readable by unprivileged applications. [S10]
+- Kernel errors and existing EDAC/RAS evidence: distinguish corrected errors from uncorrected/fatal errors and report available history. EDAC documentation explicitly says corrected errors may, but need not, predict later uncorrected errors. Missing reporting hardware/driver is unknown. Kernel log access can require `CAP_SYSLOG` when `dmesg_restrict=1`; do not assume systemd/journald on Void or other distributions. [S13][S19]
+
+Kernel or mount optimizations should be suggestions tied to an observed limitation and a documented tradeoff, recorded for subsequent comparable runs. This research supports observing current settings and thermal/power/error evidence; it supplies no evidence for blanket scheduler, write-cache, governor, or filesystem changes.
+
+## Remaining decisions and evidence gaps
+
+The next human decisions are the ordinary run's write authorization/budget, minimum free-space reserve, workload lengths and repetitions, required versus optional queued/sync/verification tests, how reduced-capability results affect score eligibility, the supported transport list, the privilege interaction, and the exact advice wording. A sustained-media profile would need a separate impact budget.
+
+Implementation work will need parser fixtures from supported smartctl/nvme-cli versions; success, partial and denied-permission results; real ATA/NVMe/USB/RAID samples; healthy and failing vendor examples; and proof of cancellation, space reservation, direct-I/O handling and cleanup across filesystems. No such hardware validation occurred here. No calibrated cross-device replacement thresholds or modern SSD remaining-life model were found or claimed.
+
+Context7 library resolution succeeded for fio, smartmontools, nvme-cli, Linux kernel, GNU Coreutils and QEMU. Both allowed nvme-cli documentation fetches returned “Could not fetch documentation snippets”; its official released documents and source were inspected instead. The NVM Express specifications landing page returned HTTP 403, so NVMe field semantics here are grounded in maintained libnvme definitions and smartmontools implementation rather than a directly retrieved current specification PDF. Those are material evidence limits, not silently filled gaps.
+
+## Sources inspected
+
+- **S1:** [fio 3.43 HOWTO](https://github.com/axboe/fio/blob/fio-3.43/HOWTO.rst), relevant workload, size/runtime, buffering, engines, percentile, verification and error sections; [release](https://github.com/axboe/fio/releases/tag/fio-3.43).
+- **S2:** [smartctl manual source](https://github.com/smartmontools/smartmontools/blob/master/smartmontools/smartctl.8.in), health, attributes, JSON, exit status, device transports, standby and self-tests.
+- **S3:** nvme-cli v3.1 [SMART log command](https://github.com/linux-nvme/nvme-cli/blob/v3.1/Documentation/nvme-log-smart.txt), [global options](https://github.com/linux-nvme/nvme-cli/blob/v3.1/Documentation/global-options.txt), [legacy alias](https://github.com/linux-nvme/nvme-cli/blob/master/Documentation/nvme-smart-log.txt), and [release](https://github.com/linux-nvme/nvme-cli/releases/tag/v3.1).
+- **S4:** [smartmontools NVMe support examples](https://www.smartmontools.org/wiki/NVMe_Support), inspected through Context7.
+- **S5:** [libnvme types](https://github.com/linux-nvme/libnvme/blob/master/src/nvme/types.h), `nvme_smart_log` and `nvme_smart_crit` documentation.
+- **S6:** [smartmontools NVMe JSON implementation](https://github.com/smartmontools/smartmontools/blob/master/smartmontools/nvmeprint.cpp).
+- **S7:** [Linux man-pages open(2)](https://man7.org/linux/man-pages/man2/open.2.html), exclusive creation and direct/synchronized I/O.
+- **S8:** [Linux PSI documentation](https://www.kernel.org/doc/html/latest/accounting/psi.html).
+- **S9:** [Linux I/O statistics documentation](https://www.kernel.org/doc/html/latest/admin-guide/iostats.html).
+- **S10:** [Linux hwmon sysfs interface](https://www.kernel.org/doc/html/latest/hwmon/sysfs-interface.html).
+- **S11:** [Linux tmpfs documentation](https://docs.kernel.org/filesystems/tmpfs.html).
+- **S12:** [Linux VM sysctl documentation](https://docs.kernel.org/admin-guide/sysctl/vm.html), `drop_caches`.
+- **S13:** [Linux RAS documentation source](https://www.kernel.org/doc/html/latest/_sources/admin-guide/RAS/main.rst.txt), error categories and EDAC.
+- **S14:** [GNU Coreutils dd manual](https://www.gnu.org/software/coreutils/manual/html_node/dd-invocation.html).
+- **S15:** [smartmontools drive database](https://github.com/smartmontools/smartmontools/blob/master/smartmontools/drivedb.h), default and model-dependent attribute mappings.
+- **S16:** [Google, Failure Trends in a Large Disk Drive Population](https://research.google/pubs/failure-trends-in-a-large-disk-drive-population/), primary publication abstract, 2007.
+- **S17:** [QEMU NVMe implementation](https://github.com/qemu/qemu/blob/master/hw/nvme/ctrl.c), `nvme_smart_info`; [NVMe device documentation](https://github.com/qemu/qemu/blob/master/docs/system/devices/nvme.rst), inspected through Context7.
+- **S18:** [Linux NVMe ioctl authorization](https://github.com/torvalds/linux/blob/master/drivers/nvme/host/ioctl.c).
+- **S19:** [Linux kernel sysctl documentation](https://www.kernel.org/doc/html/latest/admin-guide/sysctl/kernel.html), `dmesg_restrict`.