[Bug]: Dashboard — a disk whose health cannot be read is reported as "degrading"

[laurentiu021]

Problem

A machine whose drives are listed but report no SMART data is told its disk health is degrading. Nothing is degrading; nothing was measured.

HealthScoreService marks the disk component unavailable only when the list is empty:

if (disks is null || disks.Count == 0) unavailable.Add(DiskComponent);

A drive with no SMART data still produces a DiskHealthReport — HealthPercent is documented to return null in that case — so the list is non-empty, the component is not marked unavailable, ComputeDiskScore returns the deliberate 80 for unknown, and ClassifySmartHealth(80, unavailable: false) lands in the >= 60 branch: "Disk health degrading — check System Health", yellow.

The code already knows this is the wrong answer. DashboardViewModel.ClassifySmartHealth's own remarks say so:

Scoring it as unknown instead would put it in the "degrading" branch, which is a different wrong answer: nothing is degrading, nothing was measured.

The guard against it was written for the empty-list case only, so the present-but-unreadable case reaches exactly the outcome the remarks rule out. Not rare: consumer SATA and NVMe drives frequently expose nothing through MSFT_StorageReliabilityCounter, and a VM exposes nothing at all.

Expected behavior

Drives present but none readable is the same absence of evidence as no drives at all: the disk component is unavailable, and the Dashboard says "Disk health could not be read — see System Health" instead of naming a hardware trend it never observed.

The mixed case (one drive readable, another not) keeps the worst measured verdict, deliberately — marking the component unavailable there would mask a genuinely failing drive behind an "unreadable" message.

Evidence

• SysManager/SysManager/Services/HealthScoreService.cs — the unavailable list
• SysManager/SysManager/ViewModels/DashboardViewModel.cs — ClassifySmartHealth and its remarks
• SysManager/SysManager/Models/DiskHealthReport.cs — "Returns null when no SMART data is available"

Affected tab

Dashboard (and System Health's score)

[laurentiu021]

Fixed in v1.76.11 via #2107.

Root cause. The disk component was marked unavailable only for an empty list. A drive with no SMART data still produces a report (HealthPercent returns null), so the list was non-empty, ComputeDiskScore returned the deliberate unknown 80, and ClassifySmartHealth(80, unavailable: false) read that through its >= 60 branch as "Disk health degrading" — a claim about failing hardware on a machine where nothing was measured.

Fix. disks.All(d => d.HealthPercent is null), with the decision extracted into a pure internal static UnavailableComponents so it can be asserted without querying WMI.

All, not Any, and for two reasons. One readable drive at 20% plus one unreadable must keep reporting critical rather than "could not be read", or a failing disk hides behind the unknown message. The mutation proof then showed a second reason I had not predicted: [].Any(…) is vacuously false while [].All(…) is vacuously true, so Any would also have broken the no-drives case that already worked.

Verification. Reverting to Count == 0 reddens the new all-unreadable test (Collection: ["Memory", "Uptime"] / Not found: "Disk"); switching All to Any reddens the mixed-read test and the empty-list test. 350 cases green across the health, dashboard, disk-report, system-health and architecture suites.