Preparation Guide For macOS High Sierra Installation

High Sierra GM Candidate


There aren’t many major changes going from Sierra to High Sierra. But one of the most exciting and significant is the introduction of a new file system to replace the aging HFS+. It’s called the Apple File System (APFS). If you’d like to read more about APFS, I recommend this overview by Peter Cohen. “APFS: What You Need To Know About Apple’s New File System

If your Mac boots from an SSD, it will be automatically converted to APFS during the upgrade. Unlike the developer betas, you cannot opt out of this automatic update to APFS. Not to worry. APFS has been tested extensively on hundreds of millons of iPhones and iPads already, and it’s ready for prime time. Even if you have File Vault turned on, the conversion will occur.

If you have a Fusion drive, the installer won’t upgrade it to APFS. Some developer betas supported this upgrade for testing, but the final release of High Sierra will not support Fusion Drives.

If you boot from a standard hard disk, the installer will not upgrade the drive to APFS. For more clarifications, see this Macsales blog written by Steve Sande. “Translating Apple’s New High Sierra & APFS Compatibility Document.This Apple document says that APFS, while not optimized for hard disks, will work with them if you elect to do the upgrade later.

What About External Time Machine Drives?

You should not attempt to upgrade your Time Machine drive to APFS with Disk Utility. Time Machine only works on drives formatted as HFS+. Also, if you format a new drive as APFS for other uses, your Mac won’t recognize it as a Time Machine destination—at least for the current implementation of TM.

For some additional details, see this article by our Jeff Butts. “Time Machine and APFS: What You Need to Know.

Next page: mopping up.

Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Oldest Most Voted
Inline Feedbacks
View all comments
W. Abdullah Brooks, MD

John: I’m travelling so have not done the migration to High Sierra. Plus, I’m in the midst of tight deadlines and cannot afford the downtime – maybe this weekend. That said, I did check the Roaring Apps web site, and my first search drew a blank. I probably am not in a highly serviced profession, but I asked about Endnote X8.1, which is mission critical for me as we speak. Roaring Apps did not have the app in its list. My next search was for Stata – again, crickets. I’m definitely an typical Apple client insofar as that site is… Read more »


The first step in this process is to decide if you even want to upgrade on the day High Sierra is released.

Normally I do. This time however I may wait. I mean it’s macOS 10.13. 13!. I mean they couldn’t have done like they did with the iPhone and gone from macOS 10.12 to X.XIV? No it’s 13 released just before Halloween.

Really asking for it they are.