Want to know How to Fix Mac '-123 not an HFS volume' Error ? Mac hard drives functions on the hfs partition and Mac OS X is also installed on it. The file system is very well developed but there are certain situations where the files system gets corrupted. The causes of corruption are many like header or catalog file damage, abrupt system shutdown, power surge, partitioning or formatting error or any other. When you are getting the error you can not access any data of the drive or save any new file in it so the solution of How to Fix Mac '-123 not an HFS volume' Error is necessary. You can take help of disk utility to detect the error and fix it but on certain occasions the disk utility fails then you have to format the drive which can be done by using the same utility. After the formatting the data will be lost and you can get it back by using Time machine that saves a copy of every file in the Mac hard drive. If it does not work then use the Mac data recovery software to restore all your files. Now you know How to Fix Mac '-123 not an HFS volume' Error and recover your data.