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Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them. But don't repair/rebuild the Fusion Drive without a backup, if you are asked to. You will loose all your data.
If you have a (Time Machine) backup, you may now repair the Fusion Drive, check it for errors, quit Disk Utility, open Restore From Time Machine Backup, restore your backup data and finally reboot to the restored system.
Quit Disk Utility
Open Terminal in the menubar
Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them.But don't repair/rebuild the Fusion Drive without a backup, if you are asked to. You will loose all your data.
Quit Disk Utility
Open Terminal in the menubar
Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them. But don't repair/rebuild the Fusion Drive without a backup, if you are asked to. You will loose all your data.
If you have a (Time Machine) backup, you may now repair the Fusion Drive, check it for errors, quit Disk Utility, open Restore From Time Machine Backup, restore your backup data and finally reboot to the restored system.
Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them. But don't repair/rebuild the Fusion Drive without a backup, if you are asked to. You will loose all your data.
Quit Disk Utility
Open Terminal in the menubar
Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them
Quit Disk Utility
Open Terminal in the menubar
Backup your main volume and if necessary the volume "Untitled" on your SSD to an external backup drive.
Detach the backup drive and all other external drives
Boot to Recovery Mode by entering cmdR immediately after the boot chime.
Open Disk Utility and check all volumes and disks for errors and repair them. But don't repair/rebuild the Fusion Drive without a backup, if you are asked to. You will loose all your data.
