Mac computers use HFS as their native file system. At 24 Hour Data we have many clients that think their external hard drive has failed, because their Mac will not mount the drive. Most External Hard Drive manufacturers like Western Digital, Seagate, Hitachi, and more Pre-Format drives with Windows file systems. By default most externals are formatted FAT or NTFS.
Macs will see HFS, FAT, and NTFS. However, if you have a Mac you will not be able to write to NTFS formatted drives without a third party application. Many Mac users get a drive from Frys, Best Buy, Comp USA, and so on that is pre-formatted FAT. When they start using the drive they have no issues. This because Macs can read and write to the FAT file system just fine.
What many Mac users are finding out is that their external drive suddenly stops mounting when the plug it in or turn it on. Before you panic and call a Data Recovery company like 24 Hour Data try connecting your drive to a PC. We have found that once FAT formatted drives are connected to a Windows machine then brought back over to a Mac they work fine.
This is only a temporary fix and may have to be done several times. The long term fix is to backup your data on the drive and format the drive HFS. You can format the drive using Apple’s Disk Utility in the Utilites Folder. Be careful not to format any drive without backing up your data first.
If your drive does not mount after connecting it to a PC then you have a potential Data Recovery. Also, if you hear any unusual sounds like clicking or grinding always power down the drive immediately. 24 Hour Data offers a Free Quote for Data Recovery and a No Data, No Charge policy.