To get the most out of the new file system, learn how to format drives with APFS; create, resize, and delete containers; and create APFS volumes that have no size specified using Disk Utility. For additional information on Disk Utility or if you need to work with HFS+ (Hierarchical File System Plus) formatted drives, learn how to use Disk Utility in macOS. It is also a good idea to learn more about APFS and disk types.
Format a Drive With APFS
Using APFS as a disk format has a few restrictions you should be aware of:
Time Machine drives must be formatted as HFS+. Do not format or convert a Time Machine drive to APFS. Apple does not recommend using APFS on standard rotational hard drives. APFS is best used on solid-state drives. If you encrypt a drive using macOS High Sierra or later, the drive is converted to APFS encrypted format. Be careful when doing this, as some apps and utilities such as Time Machine do not work with the APFS format.
Here’s a look at how to format a drive to use APFS.
Convert an HFS+ Drive to APFS Without Losing Data
You can convert an existing volume to use the APFS format without losing information already present. Make a backup of your data. If something goes wrong while converting to APFS, you could lose the data.
Create Containers for an APFS Formatted Drive
APFS brings a new concept to the format architecture of a drive. One feature included in APFS is its ability to change the size of a volume dynamically to meet the user’s needs. With the older HFS+ file system, you formatted a drive into one or more volumes. Each volume had a set size determined at the time of its creation. While, under certain conditions, a volume could be resized without losing information, those conditions often did not apply to the volume you needed to enlarge. APFS does away with most of those old resizing restrictions by allowing volumes to acquire any of the unused space available on an APFS formatted drive. The shared unused space can be assigned to any volume where it is needed without worrying about where the free space is physically stored—with one exception. The volumes and any free space must be within the same container. Apple calls this feature Space Sharing. It allows multiple volumes, regardless of the file system they may be using, to share the available free space within the container. You can also pre-assign volume sizes and specify minimum or maximum volume sizes as well.
Create an APFS Container
Containers can only be created on APFS formatted drives. Here’s how: At this point, you have created a new container that includes a single volume taking up most of the space within. You can now use the Create Volumes section to modify, add, or remove volumes within a container.
Delete a Container
Follow these steps to delete a container.
Create, Delete, and Resize Volumes
Containers share their space with one or more volumes contained within. When you create, resize, or delete a volume, it is always referenced to a specific container.
How to Create a Volume
How to Remove a Volume
Resizing Is Unnecessary
Because any free space within a container is automatically shared with all APFS volumes within the container, there is no need to force the resizing of a volume as was done with HFS+ volumes. Deleting data from one volume within a container makes that newly freed up space available to all volumes. If no reserve size is set, the volume is only as large as the amount of data it contains. If no quota size is set, the volume size limit is based on the container size and the amount of space taken up by other volumes in the same container. The free space in a container is shared by all volumes.
