A sudden wave of reports last month that solid‑state drives were vanishing from both File Explorer and UEFI/BIOS left Windows 11 users alarmed — but the truth, based on community forensics and vendor testing, is more complicated than a simple “bad Windows update” narrative. (support.microsoft.com) (theverge.com)
The flashpoint for the panic was the August 12, 2025 cumulative update for Windows 11 24H2 — KB5063878 (OS Build 26100.4946) — which was followed by widely shared posts and videos describing drives that “disappeared” during large, sustained write operations. Early community reproducibility suggested a narrow failure window: targets were often drives more than ~60% full, and the failure typically showed up after tens of gigabytes of continuous writing (community tests commonly cited ~50 GB). (support.microsoft.com)
Microsoft and several SSD vendors opened investigations as the reports proliferated. Microsoft’s public service page for KB5063878 documents the update package and confirmed there were other known issues unrelated to storage (for example, some streaming/NDI performance regressions and a WSUS deployment error), but Microsoft reported that it could not reproduce a systemic storage failure linked to the update in its telemetry or internal testing. (support.microsoft.com) (bleepingcomputer.com)
At the same time, SSD controller supplier Phison conducted extensive tests and publicly reported that its validation could not reproduce the reported drives‑vanishing behavior across production firmware images, dedicating thousands of hours and test cycles to the effort. That testing, and subsequent community work, shifted attention toward a different hypothesis: that a small number of drives had been shipped with engineering / pre‑release firmware not intended for retail distribution — firmware that could exhibit edge failures when exposed to a specific host timing or workload change introduced by the update. Several outlets and community moderators reported that Phison engineers had validated the engineering‑firmware hypothesis in lab tests. (neowin.net) (guru3d.com) (windowsreport.com)
Source: Mint Baffled by missing SSD in Windows 11? Here’s what you should do urgently | Mint
Background / Overview
The flashpoint for the panic was the August 12, 2025 cumulative update for Windows 11 24H2 — KB5063878 (OS Build 26100.4946) — which was followed by widely shared posts and videos describing drives that “disappeared” during large, sustained write operations. Early community reproducibility suggested a narrow failure window: targets were often drives more than ~60% full, and the failure typically showed up after tens of gigabytes of continuous writing (community tests commonly cited ~50 GB). (support.microsoft.com)Microsoft and several SSD vendors opened investigations as the reports proliferated. Microsoft’s public service page for KB5063878 documents the update package and confirmed there were other known issues unrelated to storage (for example, some streaming/NDI performance regressions and a WSUS deployment error), but Microsoft reported that it could not reproduce a systemic storage failure linked to the update in its telemetry or internal testing. (support.microsoft.com) (bleepingcomputer.com)
At the same time, SSD controller supplier Phison conducted extensive tests and publicly reported that its validation could not reproduce the reported drives‑vanishing behavior across production firmware images, dedicating thousands of hours and test cycles to the effort. That testing, and subsequent community work, shifted attention toward a different hypothesis: that a small number of drives had been shipped with engineering / pre‑release firmware not intended for retail distribution — firmware that could exhibit edge failures when exposed to a specific host timing or workload change introduced by the update. Several outlets and community moderators reported that Phison engineers had validated the engineering‑firmware hypothesis in lab tests. (neowin.net) (guru3d.com) (windowsreport.com)
What actually happened — timeline and symptoms
How the reports began
- The earliest public reports came from hands‑on community testers and individual users who experienced drive disappearance during large writes after installing KB5063878 (and a related preview update KB5062660). Testers reported the same symptom profile repeatedly: heavy sequential writes, loss of SMART and controller telemetry, and the drive becoming inaccessible in Disk Management and Device Manager. Reboots sometimes restored visibility, but written files were often truncated or corrupted. (windowslatest.com)
- Media amplification (videos, social posts) created the widespread impression that the Windows update had “bricked” many drives. That impression was intensified by early community‑generated lists of potentially affected models. These lists were useful leads but quickly became noisy and inconsistent because firmware revisions, motherboard BIOS versions, and other host variables changed exposure. (windowscentral.com)
Key reproducible symptoms reported by multiple testers
- Drive vanishes from File Explorer, Device Manager and Disk Management mid‑write.
- SMART and vendor utility telemetry becomes unreadable or the device reports as failed.
- Some drives reappear after reboot; others remain inaccessible and require vendor tools or RMA.
- The workload pattern: sustained sequential writes on the order of tens of gigabytes, often when the drive is already substantially filled. (windowslatest.com)
Root cause: firmware edge case, hardware batch, or Windows timing change?
Multiple lines of evidence converged — but did not produce a single, simple, vendor‑issued root‑cause bulletin linking KB5063878 to mass failures.- Microsoft’s position: after investigation, Microsoft stated it found no telemetry evidence of an increase in storage failures after the update and could not reproduce the issue on up‑to‑date systems; it continued to collect user reports while working with partners. (support.microsoft.com)
- Phison’s position: Phison invested thousands of hours of testing (reported as ~4,500 cumulative hours and more than 2,200 test cycles in public statements) and said it was unable to reproduce the issue on production firmware; it also cautioned that some circulated advisory documents were fake and advised customers to follow best practices such as proper cooling. (neowin.net) (guru3d.com)
- Community forensic hypothesis: independent testers in groups such as PCDIY! found that many of the failing drives were running engineering or pre‑release firmware images — builds intended for internal testing, validation, or sampling — rather than the stable, production firmware that retail drives ship with. The hypothesis: the Windows update altered host I/O timing or behavior in a way that triggered a latent fault path or debug hook present in those unfinished firmware builds. Several outlets reported that Phison engineers reproduced the problem in lab conditions when using these pre‑release images. This narrows the exposure to a small, non‑representative set of drives rather than an OS‑wide regression affecting mass production firmware. (windowsreport.com) (theverge.com)
What to do urgently — a prioritized action plan
If an SSD you depend on has gone missing from Windows 11 or disappeared from BIOS, act deliberately: the wrong immediate move can reduce the chance of recovery.Immediate actions (first 30–60 minutes)
- Stop writing to the system — avoid further large file operations or attempted fixes that may overwrite data in place. If a drive became inaccessible during a write, continuing to use the machine risks additional corruption.
- Document/collect evidence — take screenshots, note the exact model, serial number, firmware reported (if visible), Windows build (winver), and the exact sequence of steps that led to the event. This information speeds vendor support and RMA.
- Graceful reboot — in many community reports a simple reboot restored the drive temporarily. Do not run data‑wrapping tools before you attempt to image the device if the data is critical.
If the drive reappears
- Immediately back up everything irreplaceable to another physical disk or cloud service — do not rely on system restore points or snapshots alone. Once data is safe, check vendor utility logs and SMART health, then proceed with conservative diagnostics.
If the drive remains missing in OS and BIOS
- Power down the machine, reseat the SSD (for M.2 drives) or swap cables/slots (for SATA/NVMe adapters) and attempt a boot into a clean environment (Linux live USB or vendor recovery/diagnostic image) to check whether the device enumerates at the host/NVMe level. Community forensic procedure recommends imaging the device with a read‑only tool (ddrescue or vendor imaging utilities) before attempting in‑place writes.
If data is critical
- Create a forensic image immediately (or ask vendor support for guidance). If you’re not comfortable with imaging, contact a professional data recovery service rather than performing risky operations that might write to the medium.
How to recover a visible but misbehaving SSD (step‑by‑step)
If the drive is visible but showing errors, follow a cautious, ordered sequence:- Back up critical files immediately.
- Check Device Manager, Disk Management, and vendor utility for model and firmware strings — record them. (windowscentral.com)
- Use the vendor’s official diagnostic utility (for example, Crucial’s Storage Executive or Western Digital’s Dashboard/Kitfox) to read SMART, run diagnostics, and (if advised) update firmware. Vendor tools often provide the safest path to detect and remediate controller/final firmware problems. Always backup before a firmware update. (crucial.com) (support-en.wd.com)
- If vendor tools propose a firmware update: read the vendor advisory and release notes, confirm compatibility with your exact model and controller, and proceed only after backing up. Firmware updates can fix controller bugs but carry a non‑zero risk; vendors generally recommend their tools precisely because they handle device‑specific updates. (crucial.com)
- If firmware updates are not available or diagnostics fail, gather vendor logs and open a support case with the SSD manufacturer — provide model, serial number, firmware version, Windows build, and event timestamps. Vendors may have internal tools or a preferred RMA path. (neowin.net)
Short‑term defensive tactics (if you haven’t installed KB5063878)
- Delay the update on critical systems that host large writes (video editing, content creation, virtualization hosts). Enterprises should withhold the KB from production rings and run representative stress tests in a lab. Microsoft’s KB page for KB5063878 shows the package details and other known issues, but not a universal storage failure advisory — staging and validation remain prudent. (support.microsoft.com)
- Avoid sustained high‑volume sequential writes on systems that have installed the update until you verify your device’s firmware and vendor guidance. Community reports highlight ~50 GB single continuous writes as a common trigger. (windowslatest.com)
- Inventory SSDs across fleets — gather model/controller/firmware info using vendor tools or inventory tooling (SCCM, scripts) and check vendor advisories before mass deployment.
How to uninstall KB5063878 (if you believe the update is the immediate trigger)
If you already installed KB5063878 and want to remove it temporarily, Microsoft and third‑party guides outline the removal path: Settings → Windows Update → Update history → Uninstall updates, or use DISM/WUSA commands. After uninstall, pause updates to prevent automatic reinstallation while you investigate. Microsoft has guidance for uninstalling cumulative updates and also provided a mitigation for a separate WSUS deployment error tied to the same package. Uninstall steps are straightforward but are not guaranteed to recover corruption that occurred while the update and the write overlapped — backups are the essential safeguard. (pureinfotech.com) (support.microsoft.com)Vendor tools and firmware updates — practical notes
- Use the SSD manufacturer’s official utility when checking firmware and health. Examples: Crucial Storage Executive (for Crucial/Micron drives) and WD Dashboard / Kitfox / SanDisk Dashboard for Western Digital/SanDisk devices; these utilities will identify model/firmware, provide firmware downloads and run diagnostics. Always follow vendor instructions and backup first. (crucial.com) (support-en.wd.com)
- Firmware updates can resolve controller edge cases, but they are not risk‑free. Read release notes for controlled fixes that mention host interaction, heavy‑write behavior, or Windows interaction. Where possible, perform firmware updates from bootable vendor tools or within an administrative Windows session as the vendor recommends. (guru3d.com)
- If a vendor does not list a firmware update but the drive behaves as if its firmware is non‑retail (engineering), vendor support is the correct escalation path — they can verify the firmware image and advise RMA or in‑field remediation. Community testers reported that the drives exhibiting failures often had non‑final firmware images; vendors can detect and validate that assertion. (windowsreport.com)
Enterprise guidance
- Pause automatic deployment of KB5063878 in production rings until hardware inventories are validated and representative stress testing (50+ GB sequential writes on semi‑filled drives) is performed in a lab. Use WSUS/MECM/SCCM rules to stage the roll‑out and monitor telemetry.
- Run a focused validation matrix that includes current motherboard BIOS versions, NVMe drivers, and vendor firmware revisions for all popular drive SKUs in your fleet. This is the standard, conservative approach when patching firmware or OS components that touch low‑level subsystems.
- Back up critical endpoints and schedule maintenance windows for any firmware updates recommended by vendors. Have a recovery plan should an RMA or data recovery be required.
Risks, strengths and what the evidence supports
Strengths of the current evidence:- Multiple independent hands‑on testers reproduced a consistent failure fingerprint under similar workload conditions, lending credibility to the phenomenon.
- Vendors — notably Phison — publicly invested significant test hours and engaged with community leads, showing the issue received serious industry attention even if it was hard to reproduce at scale. (neowin.net)
- Microsoft’s telemetry and vendor testing did not show a system‑wide increase in disk failures traceable to KB5063878, and for most users with retail production firmware the risk appears minimal. Official telemetry remains the gold standard for determining scaled impact. (support.microsoft.com)
- The engineering‑firmware explanation is plausible and likely explains many failures, but it is not yet (in public outlets) a universally documented vendor recall across serial ranges. That means community findings should be treated as valuable diagnostics rather than definitive product recalls. (windowsforum.com)
Final takeaways for Windows users and enthusiasts
- Back up now. That is the single most important step for anyone who values their data — independent of whether your drive model is implicated by this particular story. Backups protect against update regressions, firmware mistakes, and hardware failure equally.
- If you already installed KB5063878 and have not seen issues, there is no clear evidence you must uninstall the patch — but avoid large continuous writes on drives that are over 60% full until you’ve verified vendor firmware and health. (windowslatest.com)
- If you bought a drive at retail from a reputable channel and kept vendor firmware current, you are much less likely to be affected than hobbyist test rigs using engineering samples. Still, confirm model/firmware using vendor utilities and follow manufacturer guidance. (theverge.com)
- For power users and IT teams: inventory, stage, test, and hold where necessary. A small number of edge cases can create outsized fallout in social media and influencer channels — but careful triage and firmware validation is the right way to turn panic into a fix.
Source: Mint Baffled by missing SSD in Windows 11? Here’s what you should do urgently | Mint
