KB5063878: No Widespread SSD Failures in Windows 11 24H2

Microsoft and Phison have now all but closed the book on the late‑August panic: after weeks of community reports, lab reproductions and headlines warning that Windows 11 24H2’s August cumulative (KB5063878) was “bricking” SSDs, thorough vendor and Microsoft testing found no reproducible link between the update and mass SSD failure. BornCity’s latest post relays Microsoft and Phison’s findings and confirms the update shows no detectable impact on drives after coordinated investigation. (borncity.com) (support.microsoft.com)

Background / Overview​

The issue that prompted the alarm began as a small cluster of social‑media posts and hobbyist tests in mid‑August 2025. Those early reports described a striking and repeatable symptom set: when large, sustained sequential writes—commonly cited around the ~50 GB mark—were performed on certain NVMe SSDs (often drives more than ~60% full), the target device would temporarily vanish from Windows’ device list and, in a minority of cases, return corrupted or unreadable storage after reboot. Specialist outlets and enthusiast sites picked up the story and began compiling reproduction steps and lists of allegedly affected models. (tomshardware.com)
Microsoft published the combined servicing‑stack + LCU package KB5063878 (OS Build 26100.4946) on August 12, 2025; the KB entry lists the release contents and initially stated Microsoft was “not currently aware of any issues” with the update. That public KB remains the authoritative record of what shipped. (support.microsoft.com)
BornCity and several independent publications summarized the early evidence and recommended caution—back up data, avoid large sequential writes on freshly patched systems, and hold off mass deployment while vendors investigated. Those recommendations were pragmatic: community tests produced consistent trigger profiles and useful mitigations even if the ultimate root cause had not yet been proven. (borncity.com)

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Timeline: how the incident unfolded​

Mid‑August — first reports and community reproductions​

A Japanese hobbyist first reported disappearing SSDs during heavy writes after installing recent Windows updates. The pattern—drive vanishing from File Explorer/Device Manager, unreadable SMART, sometimes corrupted data—was reproduced by a number of independent testers and consolidated into public threads and model lists. Early coverage by Tom’s Hardware, TechSpot and other outlets amplified the claims and urged caution. (tomshardware.com, techspot.com)

Late August — Microsoft and vendors notified​

Microsoft opened an internal investigation and began collecting Feedback Hub and Support reports from affected users. Controller manufacturers and SSD vendors (notably Phison) engaged with Microsoft and community testers to reproduce the fault across large fleets of drives and controlled lab hardware. Microsoft’s service alert later stated it was unable to reproduce the storage failures in its internal testing and telemetry. (bleepingcomputer.com)

End of August / Early September — Phison’s tests and Microsoft’s conclusion​

Phison performed an extensive testing campaign—publicly described as more than 4,500 cumulative hours and over 2,200 test cycles on candidate drives—and reported that it could not reproduce the reported failures nor had received partner/customer complaints consistent with the social‑media claims. Microsoft’s follow‑up service note likewise reported no telemetry‑backed increase in disk failures linked to the update. Those vendor conclusions prompted a wave of coverage reporting that the update was likely not the root cause for the majority of reports. (tomshardware.com, bleepingcomputer.com)

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What the community saw, and why it mattered​

The observable pattern reported by community testers had three defining characteristics:

• A trigger profile of large, sustained sequential writes (examples: large game updates, mass archive extraction, cloning) often in the tens of gigabytes.
• A reproducible failure mode where the target drive temporarily vanished from the OS stack (File Explorer, Device Manager, Disk Management) and SMART/controller registers appeared unreadable to vendor utilities.
• Mixed recovery behavior: in many cases the SSD returned after a reboot; in others, the partition was corrupted or the drive remained inaccessible without vendor‑level intervention.

Those characteristics together translated into a real data‑integrity risk for workloads that rely on large single transfers or continuous write pressure. That was the legitimate reason enthusiasts, IT pros and media outlets sounded the alarm even before vendors reached conclusions. (tomshardware.com)
However, the reach of those reports—how many devices were truly affected in the wild, and whether the update itself was necessary or sufficient to cause failures—remained uncertain. Community reproductions were invaluable for creating a working hypothesis, but they were limited by small sample sizes, narrow hardware mixes and potential confounders (thermal conditions, defective batches, power issues, or firmware quirks). Those limitations ultimately influenced vendor testing priorities.

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What vendors and Microsoft actually tested and found​

Two heavyweight claims underpin the follow‑up narrative now: Phison’s inability to reproduce the issue across extensive testing, and Microsoft’s telemetry analysis showing no uptick in drive failures correlated with KB5063878 installations.

• Phison: the company reported a multi‑thousand‑hour testing campaign (reported figures: more than 4,500 hours and over 2,200 test cycles) on drives identified in community reports and did not observe the failure mode in their controlled test matrix. Phison also stated it had not received confirmed partner or customer complaints matching the social‑media descriptions. (tomshardware.com, pcgamer.com)
• Microsoft: internal reviews and telemetry analysis failed to reveal a causal connection between the August cumulative update and the types of storage failures shared publicly. Microsoft asked customers to submit additional evidence via Feedback Hub or Support when those initial reproductions were proposed; after deeper data collection and partner collaboration, Microsoft found no reproducible link. (bleepingcomputer.com)

Both organizations framed their statements carefully: inability to reproduce is not identical to a categorical denial that any incident ever occurred, but it is a meaningful weight of evidence against a systemic, update‑driven failure across the installed base.

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Technical possibilities and mechanistic hypotheses​

Even with the “all clear” headlines, the incident remains instructive because it highlights how fragile interactions can be between host firmware/OS code, NVMe drivers, controller firmware and storage device thermal/operational states.

• Host Memory Buffer (HMB) and DRAM‑less SSDs: HMB allows DRAM‑less NVMe drives to borrow a slice of system RAM for mapping tables. Changes in OS allocation policies or timing can, in theory, expose firmware edge cases on DRAM‑less controllers. Past Windows 11 24H2 rollouts included HMB‑related incidents, and community posts initially considered HMB a plausible factor. That hypothesis remains plausible as a mechanism for some reported cases but is not proven to be the causal root for the wide set of reports. (techspot.com)
• Thermal and hardware defects: Phison and some outlets reminded users that SSDs under heavier loads can throttle thermally and that defective or marginal components (power regulators, NAND die, solder joints) can fail under load irrespective of operating‑system changes. Proper cooling was suggested as prudent general practice during the testing period. Phison explicitly advised good thermal management even as it said the update was not to blame. (tomshardware.com)
• Coincidence vs. causation: Where a small group of units fail after a common date, it’s tempting to blame the update; rigorous attribution requires broad telemetry and controlled reproduction. Microsoft and Phison’s inability to reproduce the fault at scale, combined with an absence of telemetry spikes, strongly points to either isolated hardware failures or coincident conditions in the initial test rigs rather than an update‑wide regression. (support.microsoft.com, pcgamer.com)

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Evidence appraisal — strengths and limits​

Strengths of the vendor investigations​

• Scale and methodology: Phison’s reported thousands of test hours and Microsoft’s telemetry access provide coverage far beyond what hobbyists can achieve. That scale matters when distinguishing systemic regressions from corner cases or manufacturing defects. (tomshardware.com, bleepingcomputer.com)
• Cross‑industry collaboration: Microsoft’s coordination with controller makers and OEMs expedited cross‑validation and reduced the likelihood of an undiscovered, widespread regression persisting unnoticed. (bleepingcomputer.com)

Limits and remaining risks​

• Non‑public test matrices: Neither Microsoft nor Phison disclosed exhaustive test configurations, specific firmware versions, or every device batch tested. That means a narrow hardware/firmware combination could still harbor a latent issue not observed in vendors’ test sets.
• Under‑reporting sensitivity: If a small population of affected drives exists (e.g., a defective manufacturing batch), telemetry aggregation might dilute signal and prevent easy detection. That makes vendor follow‑up and direct reports from affected users still valuable for forensic closure. (pureinfotech.com)
• Community reproducibility caveats: Community tests were useful in quickly surfacing a plausible pattern, but their small sample sizes and the absence of rigorous environmental controls mean that those reproductions should be treated as indicators rather than definitive proof. Any claim that KB5063878 categorically “bricked” drives across the installed base is not supported by vendor telemetry.

Wherever a claim cannot be fully corroborated via vendor telemetry or reproducible test rigs, it should be flagged as unverified. Several early model lists and a circulated “Phison affected controllers” document have been called out as inaccurate or even fabricated; those specific artifacts should be treated with caution unless vendor‑confirmed. (tomshardware.com, tech.yahoo.com)

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Practical guidance for users and administrators​

Even if KB5063878 itself is now cleared as the likely systemic culprit, the incident reinforced several practical steps that reduce risk for sensitive workloads:

• Backup first. Back up critical data before mass update campaigns or large transfers—this is basic hygiene unaffected by the incident’s final attribution.
• Avoid very large sequential writes immediately after applying major updates until your inventory of drives and firmware is validated: split large copies into smaller batches where feasible. Early community reproductions suggested failure was more likely under continuous writes of tens of gigabytes.
• Check and apply SSD firmware from vendors. Vendors sometimes release firmware updates resolving edge‑case behaviors; keeping drives updated reduces attack surface for subtle host/firmware interactions.
• Monitor vendor advisories and Windows Release Health for any change in findings. Microsoft retains the option to reclassify an issue if new telemetry arises. (support.microsoft.com)
• Staged rollouts for enterprise. Use pilot rings and phased deployment for monthly cumulative updates—particularly for endpoints that handle heavy I/O workloads (media workstations, VDI hosts, build servers). Known‑Issue Rollback and WSUS controls remain useful levers.

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What this episode means for update trust and ecosystem resilience​

The incident is a case study in modern platform stewardship: when thousands of hardware permutations meet frequent OS servicing, observation noise is inevitable, and robust telemetry plus vendor partnerships make the difference between rumor and resolution.

• Community triage matters. Hobbyists and enthusiasts surfaced a credible symptom set quickly; that early detection focused vendor attention and produced practical mitigations for power users. Community testing remains a valuable early‑warning system.
• Scale and data matter more. Vendor telemetry and multi‑device lab testing are essential for distinguishing systemic regressions from isolated hardware failures or coincidental timing. The inability of Phison and Microsoft to reproduce the failure at scale undermines the initial attribution to KB5063878 for the broader installed base. (tomshardware.com, bleepingcomputer.com)
• Communication tone is important. Vendors and platform maintainers must balance quick public updates (to calm users) with careful technical disclosure (to avoid prematurely dismissing real but narrow faults). Microsoft and Phison walked that tightrope by publicly announcing negative findings while continuing to accept customer reports.

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Final assessment and a cautious conclusion​

BornCity’s update—that Microsoft and Phison’s tests show no detectable SSD impact from KB5063878—accurately reflects the balance of authority and evidence at this time: vendor testing and Microsoft telemetry offer strong evidence against a widespread, update‑driven SSD failure. (borncity.com, support.microsoft.com)
That outcome doesn’t erase the practical lessons learned from the weeks of investigation. The following summary points capture the most important takeaways:

• The most likely interpretation: A narrow set of early incidents were either coincidental hardware failures, environmental factors (thermal/assembly defects), or highly specific combinations that vendors could not reproduce at scale. Vendor and Microsoft testing, together with telemetry, did not find a systemic regression attributable to KB5063878. (pcgamer.com, bleepingcomputer.com)
• What remains unproven: It is still technically possible that a rare combination of firmware, hardware batch and workload could reproduce the failure. Because neither vendor disclosure nor telemetry mapping is exhaustive, affected users should continue to report confirmed, reproducible failures to Microsoft and vendors for forensic follow‑up. (pureinfotech.com)
• Short‑term posture for admins and power users: Continue with cautious staging for major updates, maintain current SSD firmware, and prioritize backups and cooling for heavy‑IO endpoints. These are durable best practices regardless of whether an OS update or hardware issue is to blame.
• Long‑term ecosystem implication: The incident reinforces the need for transparent telemetry channels and coordinated disclosure between OS vendors, controller makers and OEMs so that rare but damaging interactions can be found and patched swiftly.

In practice, the immediate crisis of “Windows 11 bricking SSDs” appears to be over: Microsoft and Phison’s extensive testing found no reproducible problem tied to KB5063878, and BornCity’s follow‑up reflects that conclusion. Still, the episode is a reminder that platform and hardware engineering operate on shared, interdependent assumptions—and that quick, careful cross‑validation between community findings and vendor telemetry is the best path to durable confidence. (borncity.com, tomshardware.com)

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Source: BornCity Windows 11 24H2: No SSD problems caused by KB5063878 after all | Born's Tech and Windows World