GoKawiilmacOS 27 drops all support for CoreStorage and encrypted HFS+ volumes
A developer reports that macOS 27 can no longer mount, convert, or erase CoreStorage and encrypted HFS+ volumes, even manually through Disk Utility or the command line. Attempts to mount these volumes return errors such as a DiskManagement disenter failure, and diskutil's unlock command falsely claims the volume is locked when it is already unlocked. The system also shows a boot-time dialog warning that macOS 28, not macOS 27, will drop support—contradicting the behavior users are experiencing now.
GoKawiil's interpretation of the reporting above, not reported fact.
Users with older encrypted HFS+ or CoreStorage drives may find that hardware they relied on becomes completely inaccessible after upgrading, with no workaround offered by Apple's own tools. The mismatch between the warning dialog's stated timeline and the actual loss of support in macOS 27 suggests either an internal communication error at Apple or an unannounced acceleration of deprecation, though the developer only speculates about the cause. This leaves affected users without a clear migration path before losing access to their data.
- macOS 27 fully removes support for CoreStorage and encrypted HFS+ volumes, blocking mounting, converting, and erasing.
- Disk Utility and diskutil commands fail with misleading or contradictory error messages when handling these volumes.
- A boot-time warning incorrectly attributes the loss of support to the upcoming macOS 28 rather than the current macOS 27.
OWC external SSD enclosure (APFS-ready) — If you're migrating off aging CoreStorage/HFS+ volumes before macOS drops support entirely, a reliable external SSD enclosure makes it easy to create a fresh APFS-formatted backup and transfer drive. OWC enclosures are well known in the Mac community for compatibility and durability, making the painful migration process a lot less stressful. Better to move your data now than get locked out when Apple pulls the plug.
See OWC external SSD enclosure (APFS-ready) on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: wadetregaskis.com, 2026-11-03
Published there as: “macOS 27 does not support CoreStorage volumes”
Read the original report → The summary and analysis above are GoKawiil's own, written from reporting by the source above. Facts and quotes belong to the original publisher.