What you can do is partition the drive (see Partition tab) into, let's say two partitions, one being HFS+ for your Time Machine backup, the other being ExtFAT or FAT-32, both of which can be read and written to by OS X, Windows and Linux. Linux may work, but the drivers for journaled HFS seem unstable, so it's not recommended to use this partition under other operating systems (so as not to screw up your Time Machine backup). If you don’t have a backup, you can’t recover files that you deleted. Windows, however, won't be able to write to this volume anymore. Time Machine, the built-in backup feature of your Mac, will automatically back up your data, including apps, music, photos, email, and documents. OS X should prompt you whether you want to set it up as a backup disk. You can now use the disk for Time Machine. Note that this will erase all data on the drive. The main challenge that astrophysicists are.

Select Mac OS Extended (Journaled), which is the default, give it a name, and then click Erase…. Wormholes, black holes, cosmic strings, and circulating light beams have all been suggested as potential solutions for time-traveling to the past. Go to Disk Utility, select the drive on the left, and then go to the Erase tab. OS X won't be able to write to NTFS partitions, and both NTFS and FAT don't support the features Time Machine needs to work properly. But this varies greatly, depending on how you use your Mac. Be sure to add the size of the data on any other drives/partitions you want to back up.

In order to use your external drive for Time Machine, it has to be formatted with HFS+ (also called Mac OS Extended). A general 'rule of thumb' is, to keep a reasonable 'depth' of backups, Time Machine needs 2 to 4 times as much space as the data it's backing-up (not necessarily the entire size of your internal HD).

Best hd for time machine