Are you searching some sort of clue to overcome from bad master directory block? Then your search will be ended here for sure. In Mac master directory block keeps various information regarding the volume. But in the same time there would be some inconvenient situation occur in it because of unexpected reasons. At this point in time you may also lose the access of important file that's why it is extremely essential to resolve bad master directory block immediately. Factors like file system damaged, OS crash, hard disk failure etc could cause erroneous condition in master directory block. So whenever you receive an error message associated to it then you should backup the volume and try disk utility for diagnosing the hard drive issue. By doing so you can fix bad master directory block. But if you forget to take the backup of volume then with Mac Data Recovery Software you can get back the data from lost volume effectively. It is the best third party program for restoring every type of file from lost, damaged or deleted Mac volume in successful way. It has robust and powerful scanning mechanism which resolves the bad master directory block with ease.