Hi
I have an iMac with 3 TB Fusion drive, recently I tried to use first aid in the disk utility and it said it could not repair the disk and suggested trying recovery mode. I booted to recovery mode and ran first aid but it said also it could not fix the disk. What are my options is there a good third party utility that can fix the error as I need to upgrade to High Sierra. Currently I am using Sierra and the computer boots and works fine.
Thanks
Ayman