How Apple File System works and what Mac admins need to know

Apple put all its eggs in a new storage basket with the release of Apple File System, its first new system in more than 30 years.

Mac administrators must get to know the ins and outs of Apple's new file system, particularly because it can help increase storage capacity.

An organized file system is critical because it helps isolate and keep track of each piece of data that an organization processes, stores it and allows users to retrieve it. The Hierarchical File System (HFS) has been Apple's standard file system for iOS and Mac hard disk drives since the 1980s; the updated version, HFS Plus, debuted in 1998. But, starting with this year's iOS 10.3 and macOS High Sierra, Apple File System (APFS) is the new standard.

Attendees at JAMF Software's annual user conference, Jamf Nation, learned what's new, how to set up APFS and how to manage storage going forward. Rich Trouton, IT technology senior consultant at SAP, shared the following information in a session at the event.

HFS vs. Apple File System

The biggest difference between HFS and Apple File System has to do with storage capacity. APFS supports more than 9 quintillion (or 9 billion billion) files, versus HFS Plus support for 4 billion on a single volume. APFS also includes support for sparse files, which help use space more efficiently.

HFS is made up of volumes in disks that are then separated into allocation blocks of storage space. The base storage unit of APFS is containers, which can support multiple storage volumes that all have access to any free space that's available. This space-sharing capability means that IT can increase or decrease volumes' capacity dynamically without relying on pre-allocated space that's set in stone for each volume. It applies to solid-state drives (SSDs), plus disk images and other types of storage.

Although macOS High Sierra still supports HFS Plus, Apple will likely phase out HFS Plus eventually, so it's a good idea to move to APFS, Trouton said.

Formatting and managing Apple File System

To use and manage Apple File System volumes, you can use diskutil, a command-line utility in macOS for managing disks and partitions.

To format the disks, start by setting up containers using diskutil commands. The Create Container command creates a storage area, but it's empty off the bat. So, you must then add storage volume to it. You can do that and also add a name to the APFS volume through diskutil again.

To grow a container to add allocated storage space when more physical space is available, use the diskutil command resizeContainer, and specify which container you want to expand. Run the diskutil List command to ensure that it increased the amount of GB.

In the Disk Utility settings page in macOS, you can also view how much space is available on each container.

A Mac with an SSD converts to APFS automatically, but others may not.

APFS cloning is also new in this file system. This process allows you to make a copy of a file or directory that uses no additional space but simply stores an exact copy of the original. That's useful in case of accidental deletion or other issues in the file system that could affect files.

"What happens if you ditch that original file?" Trouton said. "Nothing."

APFS holds on to the copied version and allows you to access and manage it like the original.

Converting from HFS to Apple File System

When a Mac upgrades to High Sierra, it may or may not be automatically converted to Apple File System, depending on the type of drive it has, according to Apple. A Mac with an SSD converts to APFS automatically, for example, but others may not.

In a manual conversion, the drive has to be unmounted to make the switch from HFS Plus to APFS. You can simply run a conversion command in diskutil to convert it over.

"This is something I was worried about, but I haven't heard too much screaming so far," Trouton said.

You can also use the command line to take APFS snapshots with the tmutil command. To access the snapshot's contents, go to the Time Machine page in macOS settings, where you will see the snapshot appear in the list of mounted drives. Snapshots are useful in case someone accidentally removes a program or file or there is something that you need to restore.

To do a file or system recovery with APFS, go to Restore in Time Machine to select boot drive and the snapshot, then choose Roll Back to restore the drive to the snapshot state. New with APFS is that, if you have a software update that requires a restart of a computer, the file system automatically creates a snapshot of itself prior to the update so that you have handy a copy of the system with all the files to make sure they're intact after the update.

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