iMac Fusion drives: No Apple File System for you. HFS+ only.

[EugW]

APFS will not be supported on Fusion drives upon High Sierra's release. Cuz, well, it's borked on Fusion drives.

https://beta.apple.com/sp/betaprogram/apfsfusion

Beta versions of macOS High Sierra made a change in the disk format of systems by converting them to use the new Apple File System. The initial release of macOS High Sierra will provide support for the new Apple File System as the default boot filesystem on Mac systems with all-Flash built-in storage. 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.

Works fine on my 2017 MacBook. I'll be upgrading my 2017 iMac with 1 TB SSD to High Sierra with APFS very soon too.

I do note though that the wording leaves it open for APFS to eventually come to Fusion drives at some later date, so there's still hope yet for you Fusion types.

Also, I don't know if what happens though if you try to install High Sierra on an iMac where the Fusion drive has been separated into SSD and HD. Anyone want to test?

 

[robeddie]

This is one of many reasons I pulled the fusion drive in my 2017 iMac and just put in a full-on SSD. APFS is designed specifically for solid state drives, so even if it wasn't borked on fusion drives, you wouldn't see any of the performance benefits of APFS anyway.
Fusion drives will soon be relics of the past and it can't come soon enough.

It's just a shame that apple insists on raping us with their way over market priced SSD options, since most people won't have the nerve to open up their imacs and do the upgrades themselves, and thus are stuck with those compromised fusion drives.
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Also, I don't know if what happens though if you try to install High Sierra on an iMac where the Fusion drive has been separated into SSD and HD. Anyone want to test?

View attachment 717951

By installing the SSD in the normal SATA slot, the original SSD portion of my fusion drive was automatically separated out and appears as a separate 28gb volume on my desktop. I did install High Sierra beta 8 on it, and it formatted as APFS and works great. It's been a great way to install and test software on 10.13 while my big drive (2TB SSD) remains on Sierra 10.12.

 

[EugW]

Ah so if you separate the Fusion drive the High Sierra Beta automatically converts it to APFS for the install?

32 GB is too small though for a primary boot drive. The 128 GB drive is acceptable though.

For me the preferable combo for my main desktop would be 256 GB + HD but that doesn’t exist, so I just splurged and got a 1 TB SSD.

It’s too bad Apple doesn’t offer dual configurable drives. I might have even gone with 512 MB SSD plus 2 TB HD.

 

[robeddie]

Ah so if you separate the Fusion drive the High Sierra Beta automatically converts it to APFS for the install?

32 GB is too small though for a primary boot drive. The 128 GB drive is acceptable though.

For me the preferable combo for my main desktop would be 256 GB + HD but that doesn’t exist, so I just splurged and got a 1 TB SSD.

It’s too bad Apple doesn’t offer dual configurable drives. I might have even gone with 512 MB SSD plus 2 TB HD.

Correct. Once you pull the sata spinning drive, the blade ssd that makes up the rest of the 'fusion' can be formatted and used however you wish.
When you install high sierra beta on it, it does automatically convert to APFS

And youre right, its too small for most uses, but big enough for what I use it for - a test bed for programs in high sierra and a boot volume i can use to run things like diskwarrior and repair the main drive.

 

[EugW]

Correct. Once you pull the sata spinning drive, the blade ssd that makes up the rest of the 'fusion' can be formatted and used however you wish.
When you install high sierra beta on it, it does automatically convert to APFS

And youre right, its too small for most uses, but big enough for what I use it for - a test bed for programs in high sierra and a boot volume i can use to run things like diskwarrior and repair the main drive.

Actually, I was asking about separating the Fusion drive into an independent SSD and HD. I was wondering if you can leave the HD there and get High Sierra to format the separated SSD for APFS, while keeping the HD on HFS+ for data. This could be an option for some with Fusion drives.

 

[WilliamG]

Actually, I was asking about separating the Fusion drive into an independent SSD and HD. I was wondering if you can leave the HD there and get High Sierra to format the separated SSD for APFS, while keeping the HD on HFS+ for data. This could be an option for some with Fusion drives.

I see no reason why that wouldn’t work. The OS would just see the SSD as the target drive for install.

 

[macomar]

Ah so if you separate the Fusion drive the High Sierra Beta automatically converts it to APFS for the install?

32 GB is too small though for a primary boot drive. The 128 GB drive is acceptable though.

For me the preferable combo for my main desktop would be 256 GB + HD but that doesn’t exist, so I just splurged and got a 1 TB SSD.

It’s too bad Apple doesn’t offer dual configurable drives. I might have even gone with 512 MB SSD plus 2 TB HD.

Yes, that would be my preference too. So I am currently testing a fusion drive made of the internal 512GB SSD and an external 4TB HD.

 

[nambuccaheadsau]

Just wait for OS X.13.2 or 3 and all will be well.

 

[EugW]

MacRumors just posted an article on this.

https://www.macrumors.com/2017/09/18/apple-files-system-no-fusion-drive-support/

 

[MjWoNeR]

Apple says APFS will not be supported on Fusion Drives "in the initial release of macOS High Sierra," which suggests support could be added for Fusion Drives at a later date after lingering bugs are worked out.

It seems it will be coming to fusion drives later on. I don't mind waiting a few more months for APFS to be honest.

 

[nambuccaheadsau]

Think Apple need to do a lot more development on High Sierra. Seeing Fusion drive Macs are being sold new, quite a gaff to release it before all the nuts and bolts are tightened!

 

[Kceb83]

Yup I just bought a new iMac last week with a 1tb fusion drive. It's going back tomorrow now. Ugh...

 

[EugW]

Yup I just bought a new iMac last week with a 1tb fusion drive. It's going back tomorrow now. Ugh...

The 1 TB is the worst of the Fusion drives anyway. It only has a 32 GB SSD.

 

[Kceb83]

The 1 TB is the worst of the Fusion drives anyway. It only has a 32 GB SSD.

I concur. The performance has been slow.

 

[Ethosik]

Think Apple need to do a lot more development on High Sierra. Seeing Fusion drive Macs are being sold new, quite a gaff to release it before all the nuts and bolts are tightened!

High Sierra will work just fine on Fusion drives. You just won't be able to get APFS. And really, why are people in such a hurry to get this new file system? Wait. A new file system is not something to rush.

 

[Jacoblee23]

I posted a topic asking about if the bad performance of fusion drives were overblown when I got one and most said that the performance was slow. I have had mine for awhile now though and have had little issues. I think people over exaggerate sometimes. This does irk me that we don’t get the new file system right away though.