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Now that every Apple laptop ships with a solid state drive, many of us are learning to live with smaller storage capacities once more. At the same time, external hard drives are cheaper and roomier than ever – which means there’s often plenty of room for backups and file storage on the same drive.
Everyone should backup their Mac with Time Machine, and ideally use offsite backup services just in case. If your Mac’s hard drive is small but your Time Machine hard drive is big, it might be worth using the drive for both backup and storage purposes.
How Time Machine Works
Typical external hard drive sizes have swelled to over a terabyte (1000 gigabytes), but many new MacBooks only come with 128 or 256 gigabytes of storage. Time Machine relies on historic backups, which means that older versions of files and items you remove are stored until a point in time when the space is required again for newer data. For this reason the more space you give Time Machine, the more space it will use.
You might not care about having extensive backups of files you deleted years ago. You might download a lot of video or other large files before moving them to external locations, and that means much of the space occupied by your Time Machine disk could be put to better use. If you only ever need an up-to-date backup of your Mac, then you too could put that gigantic hard drive to better use.
It must be said that the more you use a mechanical item, the more likely it is to fail. Hard drives have mechanical, moving parts so they do occasionally die horrible, crunchy deaths. Using your Time Machine backup as an external drive may shorten the life of your drive, as you will wear out the various moving parts quicker by performing more read and write cycles.
Technically, there’s no need to partition your hard drive because Time Machine won’t delete anything on the target drive that it didn’t put there. That said, it’s far safer to partition your drive properly and keep everything clearly separate.
Note: If you’re already using a drive for Time Machine, you will lose your older backups if you make major changes to the drive. You can make another Time Machine backup once you have partitioned the drive, but your backup history will restart from this point forward. If you were careful and saved all your important files, this really shouldn’t matter.
Partitions & Sizes
It is recommended that you choose a Time Machine destination that’s roughly two-to-four times the size of the drive you are backing up. If you don’t foresee yourself needing access to years of backups then you can reduce this as you see fit, though you shouldn’t go too much smaller than double the size of your drive.
For my own 256GB MacBook Pro, I chose a 512GB partition on a 2TB drive, leaving 1.25TB left to play with for file storage purposes.
Partitioning Your Drive
1. Connect the external hard drive you wish to use to your Mac and launch Disk Utility, either using Spotlight or by navigating to Applications > Utilities.
2. Select the drive you would like to use from the list on the left. Under the Erase tab choose “Mac OS Extended (Journaled)” and click Erase (the name isn’t important) then confirm your changes.
3. Once complete, head to the Partition tab and under the Partition Layout drop-down menu choose “2 Partitions”. Drag the divider to set the size you want, or enter it directly into the Size field.
4. For your Time Machine partition, make sure the “Mac OS Journaled (Extended)” file system is selected. “exFAT” or “Windows NT Filesystem” (if available) are both ideal for your storage partition, but you should read our guide to choosing a file system if you’re not sure.
5. Name both partitions appropriately so you know what they are, then click Apply followed by Partition in the confirmation dialogue. Once complete you’ll have two “drives” mounted instead of one.
Setting Up Time Machine (Again)
Once you’ve erased and partitioned your drive, you’ll have to point Time Machine at its new backup location:
1. Open System Preferences and choose Time Machine.
2. Click Select Backup Disk…, choose the partition you just created in the window that appears then click Use Disk.
3. Wait for your first backup to complete before disconnecting the drive. You can also now start using the drive for storage purposes, though be aware transfer speeds will be slower while Time Machine is backing up.
Better Use Your Storage
Putting your available space to better use is a simple case of analysing your demands and expectations. If you don’t need access to five years’ worth of files, and you’re careful about keeping your most precious data safe, then you probably don’t need a huge Time Machine backup. That disk space could be better put to use as external storage for media or documents, and better yet your Time Machine backup will fire each time you connect the drive.
Have you partitioned an older drive for use with Time Machine? Fill us in on your backup solutions in the comments, below.