Mac startup disk file system error can prevent you from booting in to the system and you will not be able to access your files stored in the Mac drive. You must be wanting to resolve it as quickly as possible but first know the cause of Mac startup disk file system error. This can happen if the system is abruptly shut down and the the corruption of the drive has occurred. You can try to use the disk utility which can come handy against minor corruption but if the problem is major then there is not other option than formatting the drive and then reinstall the Mac OS X again. This time you probably won't be facing the Mac startup disk file system error again but the data that was stored in that drive is lost. You can use the time machine backup which saves a copy of preferred files in the external drive. If the time machine does not work then you can use the Mac data recovery software for the restoration of each and every file that was erased while formatting. The recovery process is very simple and effective so get the software now.