Are you experiencing warning sign on start up of Mac? Then it is matter of great worry which needs to be sorted out otherwise situation could be worse than ever. Generally Mac provides quick response while startup but unfortunately occasionally there might be incident in which you will have to encounter warning sign on start up of Mac. It lets you complete restriction in the access of Mac and it is possible that your important work get affected adversely in such scenario. Hence you need to overcome from this type of condition as quick as possible. When there would warning sign on start up of Mac then it means that the system has recognized OS X but couldn't boot because of certain problems with system. According to experts advice one should try to repair volume by using disk utility to resolve this issue. You can even open the system in safe mode and then run fsck. But if all these measures failed to fix warning sign on start up of Mac then ultimately installing fresh Mac OS X through original disk is the one and only option left. But before doing so you must take the backup of Mac. In case you forget to backing up data then here comes the need of Mac Data Recovery Software which restores all your Mac data successfully.