Windows 11 KB5063878 Storage Regression Affects Phison DRAM-less NVMe SSDs

Microsoft’s August cumulative for Windows 11 (KB5063878, OS Build 26100.4946) has been tied in independent community testing and aggregation threads to a serious storage regression that can render certain NVMe SSDs inaccessible during large, sustained write operations — and administrators also faced a separate enterprise installation regression (error 0x80240069) that disrupted WSUS/SCCM rollouts. r on August 12, 2025 as a combined servicing stack and cumulative update for Windows 11 version 24H2 (OS Build 26100.4946). The public release notes list security and quality improvements and initially reported no known storage-related issues.
Within days of the rollout two distinct ped. First, enterprise admins reported an installation error — 0x80240069 — when delivering the update via WSUS or SCCM, which blocked or repeatedly failed deployments across managed fleets. Microsoft used servicing controls (Known Issue Rollback) to mitigate that distribution regression.
Second, enthusiast communities and tech outlets began reportinbecome unresponsive and effectively “vanish” from Windows during sustained, large sequential writes (community testing commonly cites the ~50 GB range as a trigger). The affected drives often present unreadable SMART data or appear as removed from Disk Management and Device Manager; a reboot sometimes restores visibility temporarily but does not guarantee data integrity.

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Overview of the storage problem​

Symptoms reported by users and testersfnager and Disk Management while a large write is in progress.​

• SMART attributes and controller information become unreadable to host tools.
• Affected systems commonly see the failurees in the tens of gigabytes (community tests cluster around ~50 GB).
• Rebootintore the drive, but the fault is often reproducible under the same workload and can leave file-system corruption.

These are not isolate independent threads and technology outlets compiled consistent reproduction steps and symptom fingerprints, which is why the issue escalated from der coverage. That said, vendor-level telemetry and a universal vendor or Microsoft acknowledgement tying KB5063878 conclusively to a specific firmware fault remained limited at the time of reporting.

Models and controller families implicated​

Community-collated lists point to an over‑representation of devices using Phison controller families and several branded models that use Phison silicon. Common and families include:

• Corsair Force MP600 (Phison E12/PS5012-E12 family).
• Drives using the Phison PS5012‑E12 / E16 family and some E31T/E21T variants.
• Kioxia Exceria Plus G4 (Phison-based SKU variants).
• Fikwot FN955 and similar third‑party branded devices reported in early threads.
• SanDVMe 3D (included in aggregated lists).

Important caveat: these lists are communiing. Firmware version, motherboard firmware (UEFI/BIOS), and workload specifics materially affect reproducibility; the model lists are investthan definitive recalls.

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Technical analysis: how and why thst Memory Buffer (HMB) and DRAM-less controller sensitivity​

Many low-cost NVMe designs are DRAM‑less and rely on the NVMe Host Memory Buffer (HMB) feature to use system RAM as a backing cache for the drive’s Flash Translation Layer (FTL) metadata. HMB ties drive behaviot OS and driver for memory allocation. Historical incidents during the Windows 11 24H2 rollout exposed how changes in HMB allocation and timing can surface latent firmware bugs; the symptoms reported now mirror those past patterns.
If the OS changes the timing, amount, or frequency of memory allocations, or if a kernel buffering path changes under heavy sequential writes, a controller can enter an unexpected state that looks like a firmware hang or crash to the host. When that happens, the device can stop answering NVMe admin commands, appear removed from the PCIe topology, and ref#r timing, and controller firmware edge cases
Modern storage stacks layer application-level buffering, OS page cache, kernel I/O scheduling, and low-level driver commands before a write reaches the SSD. Sustained sequential writes stress multiple layers simultaneously: driver queues fill, controller write buffers and flash mapping tables are exercised, and thermal/power contrations. A subtle regression in Windows’ handling of buffered writes or in NVMe driver timing can push a controller into a failure mode that otherwise only manifests under these extreme, prolonged conditions.
Two plausible root causes, not mutually exclusive, are:

• A kernel/driver regression that changes command ordering or timing and triggers latent firmware bugs.
• A firmware defect exposed by new host behavior (HMB allocation changes or altered caching semantics) that only shows up under heavy sustained writes.

Neither hypothesis was fully confirmed by vendor telemetry at the time of reporting; the community’s rent and technically plausible but still requires vendor and Microsoft cross-validation. Treat the technical narrative as a working hypothesis supported by reproducather than a closed investigation.

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Impact: data integrity, consumers and enterprise​

Consumer risk​

For home users and enthusiasts the primary. When an SSD disappears mid‑write the filesystem can be left in an inconsistent state; even if the device later reappears, files written during the failure may be corrupted or lost. Users performing heavy I/O (game installs/patches, bulk media transfers, video renders, or backups) are at heightened risk if their SSD matches the suspect profilesk
Enterprises faced two related problems. First, the WSUS/SCCM deployment regression (0x80240069) blocked the update from being installed across managed devices, creating operational headaches and potential security exposure that required Microsoft’s Known Issue Rollback to mitigate. Second, fleets containing at-risk SSDs could suffer correlated failures during mass imaging, large file distribution, or backup operations. The combined effect is operational churn and increased support v

Why this is more than a nuisance​

Storage failures that cause unreadable SMART data or device disappearance are not merely performance regressions — they are a direct threat to data integrity. Unlike simple instability that results in a kernel crash, controller-level lock-ups during active writes can create file-system corruption and force reformatting or hardware replacement in worst cases. The economic and emotional cost of unrecoverable personal data is significant for consumers, and for organizations the risk extendss, and business continuity.

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Practical guidance and immediate mitigations​

The community and tech outlets converged on pragmatic short‑term guidance that minimizes exposure while waiting for official fixes.

Actions for home users and enthusiasts​

• Back up critical files immediately to an independent physical disk or a cloud provider. Backups are the only reliable defense against drive-level failures.
• If KB5063878 is already installed and your system contains a Phison‑based or DRAM‑less NVMe SSD, avoid running large sustained writes — postpone game instalies, large media exports, and full-disk backups to the affected drive.
• Check your SSD vendor’s management tool for firmware updates; apply only vendor-recommended firmware and only after making a verified backup. Firmware flashes carry their own risk.
• If you observe the failure, power off the system and remove the drive for forensic imaging if the data is critical; do not run derations that could overwrite recoverable sectors.

Actions for IT administrators and procurement teams​

• Inventory your SSD fleet: map models, controller families, and firmware levels. Prioritize identifying DRAM‑less NVMe devices.
• Pause or stsk endpoints using WSUS/SCCM/MECM or MDM controls until vendor guidance is validated. Use Known Issue Rollback (KIR) status to confirm whether Microsoft’s servicing mitigations have beenhedule large I/O tasks (imaging, mass distribution, backups) to endpoints not yet patched or to validated hardware.
• If a drive fails in your environment, power down and isolate the device, image it fovent logs and NVMe dumps, and escalate to vendor support with exact firmware and serial information.

Registry or HMB workarounds — use with extreme caution​

Community posts recall reg in prior 24H2 incidents (for example, limiting or disabling HMB). These are performance-reducing, temporary workarounds, not fixes, and they must be lab-tested before deployment. Do not roll such mitigations broadly without vendor ad rollback plans.

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How to investigate and collect evidence if you see the problem​

• Capture Event Viewer logs (Windowplication) immediately after the incident.
• Record OS build (confirm KB5063878 / OS Build 26100.4946), NVMe driver version, firmware version from vendor tools, and the exact workload or copy command that trigg Use vendor SSD utilities to extract SMART and controller info if the device is still visible; if SMART is unreadable, photograph or screenshot the diagnostic state prior to rebooting.
• If data is critical, image the drive using a forensic tool on a quarantine system rather than attempting destructive repairs. Imaging preserves what remains for vendor analysis or third‑party rec timestamps, system logs, and the serial number/part number for any RMA — vendors frequently require this data to trace firmware or hardware anomalies.

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Critical ananesses, and accountability​

Strengths in the ecosystem response​

Microsoft’s servicing architecture includes mechanisms (KIR, staged re‑releases) that can limit blast radius for distrid vendors can issue targeted firmware updates when investigations identify firmware faults. These tools have mitigated prior 24H2-era storage incidents and were activated again for the WSUSression.
Community-driven testing and rapid aggregation of symptom patterns are also strengths: they can accelerate vendor triage and create pressure for timely remediation. Early hands-on reproductions gave vencrete workload patterns to test.

Systemic weaknesses and recurring patterns​

The repeating pattern is clear: changes in host behavior (OS, drivers, or memoose latent flaws in controller firmware across a wide variety of devices. The diversity of SSD controllers, firmware revisions, and platform combinations makes exhaustive pre-release testing effectively impossible; this inevitably produces edge cases that surface only after broad deployment. That systemic fragility places a high burden on coordinated, multi‑vendor remediation.

Accountability and the pragmatic path forward​

Blame is rarely decisive in complex hoss. The most constructive path is cooperation: Microsoft must confirm and, if necessary, implement upgrade blocks or driver-side mitigations, while SSD vendors must investigate firmware robustness and publish targeted updates. Transparent telemetry sharing ands accelerate safe resolution; historically, this combined approach resolved earlier HMB-related incidents.

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What to watch next​

• Vendor firmware advisories for implicated controller families and specific model firmware versions.
• Microsoft Release Health updates and any Known Issues entries that explicitly address storage behavior tied to KB5063878.
• Increased vendor RMA volumes or independent forensic reports that either corroborate or refute a firmware-centric root cause across multiple vendors.

When offi, follow vendor instructions precisely: back up before firmware updates, apply only vendor-signed firmware, and validate updates in a test environment before wide rollout.

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Conclusion​

The KB5063878 episode is a stark reminder that modern OS servicing touches fragile, timing-sensitive interactions between host drivers and SSD firmware. Community tests show a reproducible, high‑risk symptom set — drives disappearing during sustained writes and presenting unreadable SMART data — that dispros Phison-based and DRAM‑less NVMe devices in early reports. Until vendors and Microsoft publish confirmatory investigations and fixence for both home users and administrators is pragmatic caution: back up critical data, avoid heavy write workloads on suspect te‑management controls to stage or delay the August cumulative where inventory shows exposure.
For all systems, rigorous backups and measured patch deplt protection while the ecosystem coordinates a technical fix.

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Source: www.guru3d.com Phison Controller SSD Failures Due to Windows 11 24H2 Cumulative Update