DevBeta 3: External USB NVMe enclosure detected but block device is not created (Apple Silicon)

[edevmon]

I have one dock with two HDDs, and one SSD inside a USB 3.2 enclosure but none of this external drives will show up in Finder, neither would be listed on Disk Utility, when I plug them in. The same devices work correctly on macOS 15.7.7 on an Intel based MacBook Pro, but they don't on macOS 27 Beta 3 (M5 MacBook Air).

I investigated this issue in the terminal with help from ChatGPT, with commands like:

system_profiler SPUSBDataType

ioreg -p IOUSB -l

log show --predicate 'subsystem contains "diskarbitrationd"' --last 30m

We concluded that the external USB mass storage devices are detected by the USB subsystem, but no block storage devices are created.

This MBA M5 came with MacOS 26 pre-installed but I dislike Tahoe's UI with a passion so I created my user and inmediately upgraded to Golden Gate even before installing any software or using any external device. This leads me to think that this problem is not inherited from MacOS 26, but that Apple is working under the hood on the USB stack instead.

It was my first time sending a report through Feedback Assistant and I wonder: am I the only one with this issue?

 

[edevmon]

Hello! This is still happening to me in Developer Beta 4. Ran a new set of tests and this is my conclusión (translation with help from ChatGPT):

Additional technical information

The affected external storage device is correctly detected at the USB level, but it never becomes available as a block storage device.

Observations​

• The USB host controller is operating normally.
• The external device is successfully enumerated as:
  
  • Vendor ID: 0x152D (JMicron)
  • Product ID: 0x0583
  • USB 3.2 (10 Gbps link)
• The USB Mass Storage / UASP stack loads correctly:
  
  • AppleUSBMassStorageInterfaceNub
  • IOUSBMassStorageDriverNub
  • IOUSBMassStorageUASDriver
• The SCSI layer is also initialized:
  
  • IOSCSITargetDevice
  • IOSCSIHierarchicalLogicalUnit

However, the initialization never progresses to creating a block storage device.

No IOSCSIBlockCommandsDevice, IOBlockStorageDriver, IOMedia, or /dev/diskX node is ever created.

As a consequence:

• diskutil list only shows the internal SSD.
• Disk Arbitration never receives a new disk to mount.
• The external drive is inaccessible.

Kernel log​

While the device is connected, the kernel repeatedly reports:

IOSCSIPeripheralDeviceType00:ClearNotReadyStatus<br>ClearNotReadyStatus in progress...<br>service response 0x2<br>task status 0x2<br>sense data 0x02/0x04/0x01<br>
The returned SCSI sense codes correspond to:

• Sense Key: 0x02 — NOT READY
• ASC: 0x04 — Logical Unit Not Ready
• ASCQ: 0x01 — Becoming Ready

The device appears to remain indefinitely in the "Becoming Ready" state and never transitions to READY, preventing macOS from publishing a block device.

Additional observations​

system_profiler SPUSBDataType unexpectedly returns an empty result:

system_profiler SPUSBDataType<br>
and

system_profiler SPUSBDataType -xml<br>
produce an empty SPUSBDataType array, despite the USB device being fully visible in ioreg and correctly enumerated by the USB stack.

Expected behavior​

The device should transition from IOSCSIHierarchicalLogicalUnit to IOSCSIBlockCommandsDevice, followed by creation of IOBlockStorageDriver, IOMedia, and a corresponding /dev/diskX device, allowing Disk Arbitration to mount the volume.

Additional information​

The same external storage device works correctly on another Mac, suggesting this may be a regression specific to the current macOS beta rather than a hardware issue.