KB5063878: Windows 11 SSD Failures Under Heavy Write Workloads

Microsoft’s August cumulative for Windows 11 (KB5063878) shipped as a routine Secure Boot and quality update, but a scatter of user reports — concentrated in Japan and amplified across enthusiasts’ channels — now link the patch to serious SSD failures under heavy write workloads; the pattern reported so far is specific, repeatable in some hands, and alarming because it can render drives inaccessible and eliminate SMART telemetry, a critical window into drive health.

Background​

KB5063878 was published on August 12 as the August cumulative for Windows 11 version 24H2 (OS Build 26100.4946). The update was framed around security and quality improvements, and included changes tied to Secure Boot certificate handling to address certificates that will begin to expire in mid‑2026. Administrators and consumers alike saw the patch roll out automatically as part of Patch Tuesday, and it superseded earlier preview fixes issued in July.
Within days of the release a Japanese PC enthusiast published methodical test logs showing a reproducible failure mode: after writing a large block of data (roughly 50 GB or more) to certain NVMe and SATA SSDs that were at moderate-to-high capacity (reportedly around 60% full), the drives would disappear from the operating system. In many cases the operating system could not read the partition table, SMART data became unavailable, and access to files on the drive was lost. Some drives recovered after a reboot; others remained inaccessible and required deeper intervention.
Multiple independent outlets and community sources picked up the reports and reproduced aspects of the behavior on a selection of drives. The testing pointed to a non‑uniform failure surface: some SSD models (and particularly those using certain Phison controllers) showed a higher incidence of failure during long, sequential write operations, while other popular models appeared unaffected.
Microsoft’s official KB/patch note for the update did not list this behavior as a known issue at the time the patch was published. Separately, Microsoft acknowledged and later resolved an unrelated enterprise installation problem (error 0x80240069) affecting WSUS/SCCM deployments of the update, but the SSD reports remained externally observed and not immediately validated by Microsoft’s public guidance.

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What users are reporting​

• A long, continuous write operation — copying or installing a large game or moving a large archive — completes or is in progress, then the target SSD “vanishes” from Windows.
• After a restart, Windows either cannot mount the partition or shows the drive as uninitialized; SMART data is often inaccessible from typical utilities, indicating the OS can no longer communicate normally with the controller.
• Some users report data corruption where file reads fail or folders are empty even though capacity indicates used space.
• Reproduction parameters reported by an experienced tester include writing ~50 GB on drives that are ~60% full. Not every drive or controller responds the same way; some fail immediately under these conditions, others are stable.
• A preliminary list of affected drives compiled from user tests includes several consumer models and controller families — notably devices that use Phison controllers — while other widely used SSDs appear to be unaffected.

These reports were initially concentrated on social platforms and niche tech blogs and then spread to broader tech press as more anecdotal confirmations surfaced.

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Technical symptoms and what they imply​

SMART and NVMe telemetry disappearance​

When SMART or NVMe Identify/SMART data becomes inaccessible, it usually indicates that the host OS can no longer successfully communicate with the drive’s controller. That symptom can arise from several root causes:

• Controller firmware crash or lock-up that stops responding to NVMe/SATA commands.
• Kernel‑level I/O stack regression that mishandles long sequential writes and puts the device driver into an unrecoverable state.
• A failing or reset PCIe/USB/SATA link that leaves the drive invisible at the bus level.
• A storage stack interaction (OS driver + filter driver + vendor driver) that disrupts command sequences, causing the controller to enter a protective state that the OS interprets as device removal.

The reported pattern (device disappears during long writes) points toward either a controller firmware or a host-side regression affecting how extended sequential write operations are processed. Because SMART information stops being readable, the problem appears to be at or below the controller level rather than a simple file-system corruption.

Why some controllers (e.g., Phison) might be more affected​

Controller vendors implement different firmware and command handling strategies for wear leveling, caching, and handling sustained sequential writes. If a host change causes a subtle timing or command pattern difference — for example, a different write-flush ordering, new SCSI/NVMe command semantics, or an altered power state interaction — certain firmware stacks could run into unhandled conditions.
That doesn’t mean the controller manufacturers are necessarily at fault; the regression could be introduced by the OS update, third‑party drivers, or an interaction between the OS and specific controller firmwares. The non‑uniformity of affected models across vendors suggests a compatibility/interaction issue rather than a widespread hardware defect.

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Verified facts and uncertainty​

• Verified: KB5063878 was released on August 12 as the cumulative update for Windows 11 version 24H2, OS Build 26100.4946. The update includes Secure Boot certificate-related changes and other quality fixes.
• Verified: Microsoft acknowledged separate installation errors affecting enterprise WSUS/SCCM workflows and provided a Known Issue Rollback / guidance for administrators; that issue was later resolved.
• Corroborated by multiple independent reports: Several community sources and tech outlets reported SSD failures occurring after the update during long write operations. Multiple independent testers captured similar symptoms and compiled lists of devices that failed under test conditions.
• Vendor engagement: At least one controller vendor publicly stated they were investigating the issue and working with partners; manufacturer-level responses vary and full vendor validation was not uniformly available at initial reporting.
• Unverified / caution: At the time of initial reporting Microsoft had not publicly acknowledged a systemic SSD failure issue tied to KB5063878. The body of reports is substantial enough to be meaningful, but it remains geographically and numerically limited compared to the total install base. The claim that KB5063878 definitively “bricks” SSDs in general is not proven as a universal effect and should be treated cautiously. Some drives and platforms have not shown any problem.

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Who is most at risk​

• Systems with SSDs that are already at moderate to high capacity (the reported tester used ~60% fullness in reproduction).
• Workloads that perform large sustained sequential writes (game installs, large archive extraction, video work, backups to local SSD).
• Machines that use SSDs with controller firmware variants observed in the initial reporting (notably, several Phison-based models were flagged more frequently).
• Users who do not have recent backups and who run large installs or transfers shortly after installing the update.

Conversely, casual users who perform smaller, intermittent writes are less likely to trigger the edge case that has been reported so far.

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Recommended immediate actions for users​

• Back up important data now. If you rely on an SSD for critical storage, copy essential files to a different physical drive or to cloud storage immediately.
• If you have NOT installed KB5063878 and want to minimize risk, consider pausing Windows updates temporarily until vendors and Microsoft provide a definitive fix. Use Settings → Windows Update → Pause updates, or use your enterprise management tools to delay deployment.
• If you HAVE installed KB5063878:
• Keep Windows Update enabled so when Microsoft releases a fix it will be applied automatically.
• Avoid running large, sustained write jobs (installing large games, mass file copies, extended archive extraction) to any drive that is known to be on a risk list or is reaching high capacity.
• If you must perform large writes, do them on a different drive (external SSD/HDD) that is not affected or on cloud storage.
• Obtain and apply the latest SSD firmware and vendor tools. SSD vendors occasionally publish firmware updates that change controller behavior in ways that improve robustness; check the drive manufacturer’s toolbox or support site for updates and advisories.
• If you encounter the issue:
• Power down the PC and cold‑start it (fully power off, wait 30 seconds, power on). In some cases the device becomes accessible again.
• If the drive remains invisible, check Device Manager, Disk Management, and Event Viewer for I/O errors or device removal messages.
• Use vendor utilities (or NVMe vendor tools) to probe the drive; if SMART is unreadable, avoid repeated risky operations and collect logs/screenshots for support.
• Report the issue via the Windows Feedback Hub and to the SSD vendor; include model, controller, firmware version, Windows build, and a step-by-step account of what you were doing when the failure occurred.
• If data is critical and the drive shows unrecoverable behavior, consult professional data recovery services rather than repeatedly forcing operations that could worsen corruption.

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Diagnostic checklist (technical)​

• Confirm installed Windows build (winver or Settings → System → About).
• Record the SSD model, capacity, reported controller, and firmware version (use vendor toolbox or standard tools).
• Attempt to read SMART/NVMe Identify using vendor tools or utilities such as CrystalDiskInfo, manufacturer’s SSD utility, or NVMe command-line tools.
• Check Event Viewer (Windows Logs → System) for entries related to nvme, storahci, disk, or kernel‑power around the failure time.
• If visible, run chkdsk on the partition; only do this if the drive is mounted and stable — running chkdsk on a drive with hardware or controller-level failure can exacerbate damage.
• Capture system logs and attach them to Feedback Hub and vendor support tickets.

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Recovery and longer-term remediation​

• Firmware updates: Manufacturers may release firmware revisions that improve controller resilience to specific command sequences. Keep vendor utilities up to date.
• Driver rollbacks or updates: In some cases a host-side driver (storage driver, NVMe filter driver, or vendor-provided driver) might interact poorly with the update. Test with the native Microsoft NVMe stack or the vendor driver if that becomes recommended.
• Microsoft patch: The cleanest remediation is a Microsoft update that removes the regression or adjusts behavior in the host storage stack. If Microsoft confirms a regression, expect a cumulative hotfix or a Known Issue Rollback (KIR) delivery through Windows Update for affected versions.
• Enterprise response: Organizations should delay rolling KB5063878 widely via WSUS/SCCM until testing completes. If the update is already deployed enterprise‑wide, prioritize systems with write‑heavy workloads for rollback or mitigation until vendor guidance appears.

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How this could have happened: a technical analysis​

Operating system updates touch low-level kernel components, device drivers, and I/O subsystems. Even a small change in how write‑back caches are flushed, how asynchronous commands are issued, or how power state transitions are handled can change the timing and sequencing of NVMe/SATA/USB commands seen by the controller. Controller firmware must be robust to corner-case host behavior, but firmware also optimizes aggressively for throughput and may assume timing characteristics that change when the host alters its behavior.
Potential root causes include:

• A regression in the OS storage stack that mishandles large sequential writes and puts controllers into states they did not expect.
• A change that alters queuing or flush semantics forcing controllers into pathological behavior under long sustained writes.
• A side-effect of Secure Boot or certificate update logic interacting with storage drivers or filter drivers, though the available symptom set more strongly indicates an I/O/regression rather than a Secure Boot failure alone.
• A rare interaction between a vendor filter driver (installed by OEMs or SSD tools) and the updated kernel components, creating an incompatible sequence of commands.

At this point, the preponderance of evidence points toward a host-side regression that surfaces with specific controllers and under defined workload characteristics — rather than a mass hardware failure.

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What vendors and Microsoft need to do (and what they appear to be doing)​

• SSD controller vendors should audit firmware for error-handling on long, sequential write workloads and add defensive checks to prevent controller lock-up or invisible failsafe states.
• SSD vendors should publish model‑specific advisories and firmware updates where a problem is demonstrated.
• Microsoft should (and typically will) investigate kernel and driver changes shipped in the patch to identify regressive behavior, publish guidance for administrators, and issue a fix if a regression is found.
• In parallel, vendors and Microsoft should coordinate on reproducing test cases and provide an official test matrix so administrators can validate systems before re‑deployment.

Initial public reaction from controller vendors indicated awareness and engagement with partners; Microsoft publicly acknowledged unrelated WSUS/SCCM install issues and has mechanisms (Known Issue Rollbacks, hotfixes) to mitigate urgent regressions once validated. The SSD reports, however, required technical reproduction and vendor confirmation before a formal KIR could be expected.

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Risk assessment: what’s the worst-case and how likely is it?​

Worst-case: data loss on drives that become inaccessible and require low-level reformat or controller-level repair, with the possibility the drive may be bricked or need RMA. For users with no backups, that data loss is acute.
Likelihood: current evidence shows the issue is real in a subset of environments and workloads, but not universal across the Windows user base. The majority of systems running the update show no immediate symptoms, indicating this is a targeted regression hitting particular controller/firmware/occupancy/workload combinations. That said, the practical impact for those affected is severe, so cautious behavior is justified until the root cause is resolved.

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Practical guidance for WindowsForum.com readers​

• Prioritize backups: local, external, or cloud — don’t assume any single drive is immune.
• If your workflow includes frequent large writes (game installations, video editing, VM images), delay installing the KB if you can, or perform those writes on a separate, unaffected drive.
• Check whether your SSD vendor has published a firmware advisory. If your vendor provides a tool that reads controller telemetry robustly, use it to capture model and firmware details now.
• Enterprises should hold the update in test rings, prioritize endpoints that match the observed failure profile for targeted testing, and coordinate with OEM and controller vendors before broad deployment.
• If you encounter a failure, collect logs, reproduce steps if safe to do so, and report thoroughly to both Microsoft (Feedback Hub) and the SSD vendor to aid diagnosis and patch prioritization.

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Conclusion​

The KB5063878 situation is a reminder that even routine security and quality updates can have unexpected interactions with complex hardware and firmware ecosystems. The reports tying the August cumulative to SSD failures under large sequential write workloads are sufficiently consistent and technically specific to merit immediate attention: back up data, avoid high‑volume writes on potentially affected drives, and defer the update if you haven’t installed it yet and cannot tolerate risk.
At the same time, readers should note the difference between localized, reproducible failure modes and a universal “bricking” event. The problem appears limited to specific hardware/firmware combinations under defined workloads. That nuance is important — it shapes a pragmatic response: protect your data now, limit exposure to large writes, and let manufacturers and Microsoft complete joint diagnostics and deliver firmware/patch updates rather than rushing to broad uninstalls or panic.
The storage ecosystem moves fast: controller vendors, SSD manufacturers, and Microsoft have both the capability and the precedent for issuing targeted fixes. Those affected should document failures carefully, share evidence with vendors, and watch for firmware updates or a Microsoft remedial patch that directly addresses the regression. In the meantime, modern defensive practices — current backups, cautious patch deployment strategies, and vendor firmware checks — remain the best way to reduce the risk of permanent data loss.

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Source: AOL.com Windows 11’s latest update may be bricking some SSDs, users report