File system comprises a set of rules on the basis of which data is logically organized in an efficient way on your hard drive. During the process of hard drive initialization, the drive is divided into partitions with different file systems. Data storage and retrieval is done with respect to the corresponding file system.File systems are required for effective space management. They store information about which portion of the media belong to which file, all slacked and free unused space on the drive, etc. Mac supported file systems (such as HFS, HFS+) have support for directory hierarchies. Files are sorted and stored in respective directories and sub-directories. A file system also restricts or controls access to data that is either stored statically or generated dynamically.
File system has a number of responsibilities and one of the most important amongst them is to keep the data structures intact and consistent. A program may terminate abruptly without informing the file system that it has finished all its activities. File system effectively handles several other problems, such as media failures, operating system failures, soft power failures, etc.
If the underlying file system of your Mac hard drive becomes corrupt, you may run into various problems. In a similar situation, you may encounter the below given error while trying to access a volume on your drive:
“-123 wrgVolTypErr Not an HFS volume [wrong volume type error or (obsolete) operation not supported for MFS]”
Due to file system corruption, the operating system fails to recognize the volume and consequently, you face data loss. In such circumstances, you should use ‘Disk Utility’ to repair corruption in the file system. If the ‘Disk Utility’ fails to resolve file system inconsistencies, the only solution is to format the drive and reinstall Mac OS X. In order to safely recover your lost or formatted data, use competent Mac data recovery software.