Preparing your Fusion Drive Mac for the macOS High Sierra install

When you sign up for beta versions of software you agreed to the non disclosure order, i.e. no discussing. there is not a High Sierra discussion forum on this Communities board, probably will be on the 25th September when it is released.

Apple announced yesterday that when High Sierra is released then only SSDs will be converted to APFS,

Fusion and HDDs will not be converted......... as yet. https://www.macrumors.com/2017/09/18/apple-files-system-no-fusion-drive-support/

No, I was not aware of that... then why is there a HighSierra section under MacOS on this community board; it hasn't been released yet.

I can't find that section. Perhaps it is not visible to me. If you are seeing it, then post your question there.

In any event, that notification from Apple concerns the beta version of HS, not the version that is scheduled to be released to the public. Please make note of the following passage (emphasis added):

"If you installed a beta version of macOS High Sierra, the Fusion Drive in your Mac may have been converted to Apple File System. Because this configuration is not supported in the initial release of macOS High Sierra, we recommend that you follow the steps below to revert back to the previous disk format."

I wouldn't be surprised at all if erasing a Mac previously used for beta testing would be required. The instructions provided by Apple (essentially: back up / reformat / restore) make perfect sense to me.

Richard:

This message appeared in large type at the top of the first page of the beta agreement in large bold type:. ( I added the underline and Italic.

Please read the Apple Beta Software Program Agreement carefully. It represents a legal agreement between you and Apple regarding Apple's proprietary and confidential information. Please keep in mind that you should not install beta software on production or business-critical systems. We strongly recommend installing beta software on a secondary system or device, or on a secondary partition on your Mac.

In addition, further in the documents, you'll see other recommendations to back up your system. each version of the beta comes with release notes. Beta tests will add, remove and change features, and are unstable. Likely, the beta test revealed that APFS is not ready for "prime time" and production code, and therefore that featuere is not being supported in production.

Since you are not willing to assume the risks of testing, you are not a good candidate for testing software. You would be best served by sticking to public versions of MacOS / IOS only.

If you participated in the Apple Developer or public beta programs, you should know that Apple strongly discourages using your "production" device for beta testing. Regardless of whether you did or did not, you DID make a backup of your system drive BEFORE installing the beta ... right? If so, then it would be possible to restore your previous OS, and then, upgrade to the release version when it becomes available.

RichardUK wrote:

...then why is there a HighSierra section under MacOS on this community board; it hasn't been released yet.

There isn't. At least it's not listed on the site map page.

I have received a notification ...

From whom?

Sorry, but I cannot understand why this requirement wasn't identified long ago and notified users BEFORE they took part in the beta program.

Presumably, that's one of the risks of running prerelease macOS versions. Perhaps you did not know, but beta software discussions are not permitted on this site.

This is required because the new HighSierra is not compatible with APFS, which is what the fusion drives use.

If High Sierra is not compatible with APFS, then it will never be released to the public. I seriously doubt that.

There is very little Nothing about your post makes any sense. I surmise that's at least one of the reasons such discussions are not permitted on this site.