Note: Apple has produced an article that goes into detail about how to do this with recent OS versions. You'll find the article here:
https://support.apple.com/en-us/HT208496
A lot of people have been confused about how to format their backup drive as APFS (
YES, you can format regular drives as APFS), and are confused about how to get an HFS+ volume on the same drive as an APFS volume.
The new Disk Utility has some nice features, but they've buried a bunch of stuff in the UI. Here's how to do both.
Format the Whole Drive as APFS- In Disk Utility's "View" menu, "Show all devices".
- Select the drive hardware, above the existing volume, in the sidebar.
- Click the Erase button.
- Choose the "GUID" partition scheme, and the plain APFS format.
- Erase the drive.
Add an APFS partition to an existing drive- Select the external drive in the sidebar
- Click the Partition tab
- Click the "+" button below the partition diagram
- Size the volume as needed
- Choose the APFS format
- Click Apply
Add a new APFS volume to an existing APFS container- Select an APFS volume in the sidebar that's in the container you want to add to
- Select "Add APFS Volume" from the Edit menu
- Select the options you want, including minimum and quota sizes if desired, and click Add
For older OS versions (pre-10.11), the following should help beyond what Apple has provided.
It's very important to properly initialize a drive if you want to be able to use it as a startup drive - whether it's a new backup drive or a new internal drive.
Most drives come set up for Windows, and while they'll
generally work with the Mac, they won't work properly as startup drives.
A "partition scheme" is the low-level on-drive stricture that is used by the OS to find the "volumes" (the "drives" that appear in Finder*a physical disk can have one or more) on a physical disk. There are three different "partition schemes" that can be used on the Mac:
- Master Boot Record*this is the partitioning scheme used by Windows, and how most drives are shipped.
- Apple Partition Map*the original partitioning scheme used by the Mac, required for Power PC based Macs.
- GUID (aka GPT)*the new partitioning scheme used by Intel Macs.
So, here's what you should do with a new drive.
Note: partitioning normally erases a drive. If you have a drive that's using the wrong partition scheme, iPartition, from Coriolis Systems, can change the partition scheme without deleting the data, and can also repartition drives with data in place.
- Start Disk Utility (it's in /Applications/Utilities)
- Select the external drive hardware in the sidebar.
You must select the drive hardware, above any existing volumes, or the Partition tab will not appear.
- Click the Partition tab
- Use Disk Utility's controls to divide the drive as needed, even as a single large partition. Use "Mac OS Extended (Journaled)" as the format type and name appropriately
- Click the Options button
- Choose the proper partition scheme (GUID for Intel macs, Apple Partition Map for Power PC) and accept the page
- Click Partition.
That's all there is to it!