Moreover, the corruption may not allow you to copy & paste all the files from the disk.
2) Fix Mac hard drive using FSCK You might have luck with FSCK command line.
Verify and Repair volume “disk1s2” Checking Journaled HFS Plus volume.
Invalid key length Invalid record count Catalog file entry not found for extent The volume could not be verified completely. Updating boot support partitions for the volume as required. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.
The steps I took to reestablish a connection with my Drobo are as follows: (This tool should only be used if no other tools such as Disk Warrior and Tech Tool Pro can see the drive AND the drive does not mount) For the symptoms I mentioned in previous post, almost immediately the Drobo mounted on the desktop with what appeared to be the correct file structure.1) Backup Data You can try copy and paste all files from the corrupt external or internal hard drive to another destination.But doing this may also result in copying errors to another location.There are many step-by-step guides on the internet that explain how to add an SSD to an existing Mac, and create a 'Fusion Drive' that has the speed of an SSD, but also the capacity of a Hard Drive.All these guides fall short in one way that was important to me.