How to create a second partition on an external disk and is it safe?

Solution 1:

Yes you can repartition without losing data. Using Disk Utility, perform a repair on your drive to make sure the drive is free of errors (even better, use Diskwarrior if you have a copy). Then unmount your drive but don't eject it. Select the drive in the left hand pane, then go to the Partition tab. On the Partition Layout section click on the "+" to create a new partition. Optionally you can specify the new partition size. When you're happy hit the Apply button and wait.

If you've absolutely critical data on the drive make sure you have a backup (which you should have anyway) but I've done this many times without an issue.

Solution 2:

The reason that everyone always harps on creating a backup before running any kind of partition command is that if something goes wrong, then generally every thing is gone. I have preformed this kind of operation on PC's many times, generally it has gone well, but the two times over the years the process glitched the partition table was destroyed. Once I was able to purchase a low level sector recovery tool to get files out that way, the other I had backups and just relied on them.

If you don't have any backups, and you preform a partition re-size, and there is a problem, you better hope for either backups, or plan on paying for data recovery.

Good luck.

Solution 3:

When i try to create a partition on external after unmounting by clicking the unmount tab in disk utililty the + symbol is greyed out. What am i missing? Thank you

"Yes you can repartition without losing data. Using Disk Utility, perform a repair on your drive to make sure the drive is free of errors (even better, use Diskwarrior if you have a copy). Then unmount your drive but don't eject it. Select the drive in the left hand pane, then go to the Partition tab. On the Partition Layout section click on the "+" to create a new partition. Optionally you can specify the new partition size. When you're happy hit the Apply button and wait.

If you've absolutely critical data on the drive make sure you have a backup (which you should have anyway) but I've done this many times without an issue."