Microsoft is currently investigating reports that the recent Windows 11 update KB5063878 is causing Solid State Drives (SSDs) to disappear from systems, potentially leading to data loss and system instability for users. The issue appears to be affecting some users after installing the Windows 11 24H2 update.

The Problem

Users have reported that their SSDs, and in some cases HDDs, are no longer being detected by their systems after installing the update. The issue seems to occur during heavy data writes, especially when transferring files larger than 50GB to drives that are over 60% full. Some users have also reported system freezes and crashes. In some instances, drives have become completely unresponsive, showing up as unallocated space. The исчезновение of the drive can occur in File Explorer and even in the BIOS.

One user on X, @Necoru_cat, conducted tests that indicated the issue arises "on SSDs with over 60% usage after approximately 50GB of continuous writing". This can be problematic when installing large software packages or PC games.

Microsoft's Response

Microsoft has acknowledged the reports and is currently investigating the issue with its partners. A Microsoft spokesperson stated, "We're aware of these reports and are investigating with our partners". However, after initial investigations, Microsoft stated, "After thorough investigation, Microsoft has found no connection between the August 2025 Windows security update and the types of hard drive failures reported on social media". Despite this, they continue to monitor feedback and will investigate any future reports.

Potential Causes

While the exact cause is still under investigation, some reports suggest that the update may be conflicting with SSD/HDD firmware or drivers, particularly during heavy write operations. It's also possible that the update is misconfiguring disk drivers or controllers, leading to the drives becoming inaccessible. One theory is that Windows 11 KB5063878 might have introduced an OS-side caching or buffering fault in the storage stack, causing the OS to hold too much data in its buffered region during long and contiguous writes. This could lead to the kernel mishandling flush/FUA ordering and I/O queues bloating, especially when the drive is over 60% full.

Affected Drives

The issue has been reported on various SSD models, including Corsair Force MP600, Maxio SSD, SanDisk Extreme Pro, Kioxia Exceria Plus G4, and Kioxia M.2 drives, as well as those with InnoGrit and Phison controllers. One tester, NichePCGamer, published a 21-drive matrix that showed failures were most frequent when controller utilization exceeded 60% during continuous writes.

User Recommendations and Possible Fixes

The PC community is advising users to avoid the update until a fix is available. Some users have suggested that restarting the PC can temporarily restore the visibility of the vanished drives. Other potential fixes include updating storage drivers/firmware from the manufacturer's website and using the Microsoft Update Catalog to manually download drivers if Windows Update fails.

If the SSD or HDD has disappeared, EaseUS Partition Master can potentially help manage and repair storage devices. It can repair disk and partition errors, recover missing partitions, and back up or clone drives.

Phison's Stance

Phison, a manufacturer of NAND controllers, has also investigated the issue. The company dedicated over 4,500 hours of testing across the reported drives and conducted over 2,200 test cycles but was unable to reproduce the reported issue. They also stated that no partners or customers have reported the issue impacting their drives. Despite these findings, Phison is still committed to supporting its customers and advises using heatsinks with high-performance drives to prevent thermal throttling.

What to Do

Until a root cause is identified and addressed, users with hard drives that are over 60% full are advised to avoid downloading, copying, or writing large files. Users should also back up important data and monitor vendor and Microsoft advisories for SSD-specific firmware, driver, or OS fixes.