Troubleshooting macOS Sequoia Installation on iMac 27” (2013) with Dual SSD Setup Using OCLP

If you’re experiencing issues upgrading to macOS Sequoia on your 2013 iMac with both a 4TB SSD and a leftover 128GB blade SSD, here are some steps to resolve the "drive not compatible" error. Since you have OCLP (OpenCore Legacy Patcher) installed, macOS Sequoia should technically be compatible, but dual-drive setups, especially with a previous Fusion Drive configuration, can sometimes cause compatibility issues.

Steps to Resolve macOS Sequoia Installation Issue

1. Verify Drive Configuration in Disk Utility

• Open Disk Utility to ensure that both drives (4TB SSD and 128GB blade SSD) are not still linked as a Fusion Drive.
• If Fusion Drive remnants are found, use Disk Utility or Terminal to separate the two drives completely.

2. Reformat the 4TB SSD

• Back up your data on the 4TB SSD.
• In Disk Utility, erase the 4TB SSD, reformatting it as APFS (GUID Partition Map). This is required for Sequoia installations.
• After formatting, try to upgrade to macOS Sequoia again.

3. Set the 4TB SSD as the Main Boot Drive

• Ensure the 4TB SSD is selected as the primary boot drive in System Preferences > Startup Disk. This may help avoid the "drive not compatible" error that may occur due to the dual-SSD configuration.

4. Remove the Blade SSD Temporarily

• To rule out conflicts with the remaining Fusion Drive component, physically disconnect the 128GB blade SSD temporarily.
• Boot the iMac from the 4TB SSD and try installing macOS Sequoia. If successful, this indicates that the blade SSD might have been causing conflicts.

5. Reinstall OpenCore Legacy Patcher (OCLP)

• If macOS Sequoia is still not installing, reinstall the latest OCLP onto the 4TB SSD after the reformat.
• Reboot and try the Sequoia installation again.

6. Install macOS Sequoia on 4TB SSD Through External Drive (if Necessary)

• As an alternative, install macOS Sequoia on an external drive to ensure it works with your hardware.
• Once successful, clone the Sequoia installation from the external drive to the 4TB SSD using Disk Utility’s Restore feature or Carbon Copy Cloner.

Conclusion

In most cases, temporarily removing the blade SSD resolves compatibility issues with macOS Sequoia on an iMac that previously had a Fusion Drive. Once Sequoia is installed, you can try reconnecting the blade SSD if you need it for extra storage.

Let me know if you need more guidance on any of these steps!