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A report by Wade Tregaskis says macOS 27, also called Golden Gate, cannot access CoreStorage volumes through normal macOS tools, including Disk Utility and diskutil. The report found that a low-level command could mount a test volume read-only, but not read-write; the findings come from one user’s testing and have not been independently confirmed here.
A report by Wade Tregaskis says macOS 27 cannot mount or manage CoreStorage volumes through normal tools such as Disk Utility and diskutil, leaving data on affected drives difficult to reach and the volumes difficult to erase. In tests described in the report, a lower-level macOS command mounted a volume read-only, but attempts to mount it read-write failed.
Tregaskis says the problem affects CoreStorage volumes, including encrypted HFS+ volumes. The report describes a 2-terabyte volume that macOS recognized as an unlocked CoreStorage logical volume, yet Disk Utility could not mount. The command-line mount attempt through diskutil also failed, reporting that the volume was locked even after an unlock command had indicated it was already unlocked.
The report says a direct call to macOS’s mount_hfs command did mount the volume when the command included the read-only option. Tregaskis was able to view files, but could not mount the volume read-write: attempts failed with a “Resource busy” error. The report also says standard erase and conversion operations failed, limiting the options for using the drive or moving its contents to another format.
Tregaskis describes a partial workaround for erasing the affected storage: deleting the CoreStorage logical volume group appears to remove its logical volume, even when the operation reports failure. After a restart, the physical volume could then be erased, according to the report. This is a destructive procedure, not a way to recover or preserve files, and the source does not establish that it will work for other volumes or configurations.
Access and Erasure Risks for Drives
If the behavior described is reproducible, people relying on older HFS+ storage could lose normal access to files after installing or using macOS 27. The report’s example suggests the issue is not simply a forgotten password: the system reportedly recognized the volume as unlocked but still could not mount it through ordinary interfaces.
The practical consequences reach beyond opening files. A drive that cannot be mounted normally may be difficult to back up or migrate, while failed erase and conversion operations can prevent its reuse. The reported read-only workaround offers a possible route to copy data, but it does not restore normal write access, and using the erase workaround would destroy the volume. Readers with important data should treat the report as a warning to maintain a separate backup, rather than assume the workaround is reliable.
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Sequoia’s Earlier CoreStorage Problems
Tregaskis says macOS 15 Sequoia had already deprecated CoreStorage and encrypted HFS+ support and made some related tools less useful. However, in the author’s experience, the volumes remained broadly usable: some needed manual unlocking at startup, and some could not be converted to APFS, but their data was still accessible.
The report characterizes macOS 27 as a more serious change because routine mounting, conversion and erasure reportedly fail. It also notes a startup dialog that warns CoreStorage volumes will not be supported by macOS 28, the next version. Tregaskis questions whether that version number is an error, but provides no confirmation from Apple. The report is an individual account, not a statement of Apple’s policy or a published compatibility notice.
Scope and Apple’s Position
The source describes one user’s testing and does not establish how many systems or drive configurations are affected. It does not identify the precise macOS 27 build, provide an independent reproduction, or include a response from Apple. It is also unclear whether the failures are a software defect, an intentional removal of support, or a combination of changes in the system’s storage tools.
The report does not establish whether the read-only mount method is safe or dependable across different CoreStorage volumes, or whether the delete-and-restart erase workaround works in other cases. The startup alert’s reference to macOS 28 also remains unexplained. Until Apple clarifies the issue or additional testing is available, the report should not be treated as proof that every CoreStorage volume will fail in macOS 27.
Watch for Apple’s Compatibility Guidance
The next useful development would be an Apple statement or support documentation clarifying whether macOS 27 is meant to support CoreStorage and encrypted HFS+ volumes, and whether the startup message naming macOS 28 is accurate. Further reports or independent tests could establish which storage configurations reproduce the mounting and erasure failures.
For now, people with CoreStorage drives should keep separate copies of important data and avoid destructive erase steps unless they intend to wipe the drive. Anyone considering a macOS update should check Apple’s current compatibility guidance and confirm that a backup is accessible before proceeding. The report does not say when Apple might address or explain the behavior.
Key Questions
What does the report say macOS 27 cannot do?
It says the usual tools, including Disk Utility and diskutil, fail to mount, convert or erase the tested CoreStorage volume.
Can the files still be accessed?
In Tregaskis’s test, a direct mount_hfs command mounted the volume read-only, allowing files to be viewed. Read-write access was not achieved, and the report does not show that this method works for every drive.
Does the report confirm that all CoreStorage drives are affected?
No. It documents one user’s tests and does not establish the scope across different drives, systems or macOS 27 builds.
Is the erase workaround a way to save the data?
No. The described workaround is for erasing the storage after deleting the logical volume and restarting. It is destructive; users should have a separate backup before attempting any erase operation.
Has Apple confirmed that support ends in macOS 27 or 28?
The source reports a startup warning naming macOS 28, but includes no Apple response confirming the warning or explaining the failures. The author raises the possibility that the version number is mistaken.
Source: wadetregaskis.com
