Windows 11 update under scrutiny as drives vanish during transfers

Users and manufacturers remain divided over whether a recent Windows 11 update is to blame for reports that some solid state and hard disk drives became undetectable during large file transfers, after controller maker Phison said it could not reproduce the problem following thousands of hours of testing. The controversy centers on Microsoft update KB5063878, released in early August, and initial reports from users in Japan who said drives went missing when attempting to move roughly 50 gigabytes or more to volumes that were about 60 percent full.

According to multiple user accounts, affected systems could temporarily restore drives after a reboot, but in some cases the devices required repartitioning or reformatting to be usable again. Early lists circulated online purported to identify dozens of affected models from manufacturers including Samsung, Western Digital, Seagate, Corsair and Crucial. Microsoft opened lines of communication asking users who experienced the issue to come forward, but media accounts said few or no users responded to that request.

Phison, whose SSD controllers are used across a wide range of drives, said it launched an extensive internal investigation...