Should I create a Fusion drive before or after updating MacOS to Mojave?

3rdShore

macrumors newbie
Original poster
Sep 30, 2017
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I've searched extensively and haven't yet found the best path forward so I'm seeking recommendations. I posted this in the "Once and for all" thread hoping it may help others who are searching for input on updates, but figure it's also a completely separate dilemma.

I'm currently running macOS High Sierra on a late 2012 Mac mini with a self installed SSD along with the original HDD NOT setup as a Fusion drive. I finally decided I'd prefer the Fusion setup for the sake of simplicity when the SSD couldn't handle the size of my current iPhone backup (and I don't want to jump through the hoops of configuring the backup to an external for the same sake of simplicity).

My question is whether I should:
-Create the Fusion drive in High Sierra and then update to Mojave?
-Update to Mojave and then create the Fusion drive (not sure if it can also be done DURING the update)?
-Create the Fusion drive in High Sierra, and don't update to Mojave?

In addition, what's the best way to clear the prior Macintosh HD drive, as it still has the older system files and an older OS, but I can't clear it from Disk Utility while booting from the newer SSD?

Of course any other suggestions are appreciated as well.
 

casperes1996

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Jan 26, 2014
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The Fusion reformats the drive, so it's impossible to maintain the OS on it while creating the Fusion.

Create a bootable installer of Mojave and do it all from it
 

3rdShore

macrumors newbie
Original poster
Sep 30, 2017
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I have a bootable installer for both Mojave and High Sierra, and my Time Machine backup is obviously created from within High Sierra, so I just wasn't sure which option would be quicker/perhaps more stable?

I assume that it may not really matter either way?
 

casperes1996

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Jan 26, 2014
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I have a bootable installer for both Mojave and High Sierra, and my Time Machine backup is obviously created from within High Sierra, so I just wasn't sure which option would be quicker/perhaps more stable?

I assume that it may not really matter either way?

The time it takes to create the fusion drive wouldn't be impacted at all.
Boot the Mojave installer and do it from there

In addition, what's the best way to clear the prior Macintosh HD drive, as it still has the older system files and an older OS, but I can't clear it from Disk Utility while booting from the newer SSD?
Not sure what you meant by this. Since the Fusion creation willr eformat the drives, it'll go away
 

3rdShore

macrumors newbie
Original poster
Sep 30, 2017
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Not sure what you meant by this. Since the Fusion creation willr eformat the drives, it'll go away
Thanks, I wasn't sure the of the intricacies of the process, and see now that it doesn't matter either way.

I've been able to create the Fusion drive, and am in the process of installing Mojave, so hopefully won't run into any bumps during the install process.
 

SketchyClown

macrumors member
YMMV, but I have found when using Mojave with my Fusion Drive, since they were supported by APFS, has been lacklustre. Spinning beach balls from hell. Horribly slow. I do enjoy having the one large drive rather than split, but it's just painful. Shouldn't use APFS on rotational drives at all IMHO. I am in the process of deciding which SATA SSD to buy to replace the old internal platter portion of the Fusion.
 

3rdShore

macrumors newbie
Original poster
Sep 30, 2017
5
0
YMMV, but I have found when using Mojave with my Fusion Drive, since they were supported by APFS, has been lacklustre. Spinning beach balls from hell. Horribly slow. I do enjoy having the one large drive rather than split, but it's just painful. Shouldn't use APFS on rotational drives at all IMHO. I am in the process of deciding which SATA SSD to buy to replace the old internal platter portion of the Fusion.
If that's the case after i update I'll have to concede that I'll be better off updating the hardware as well, but likely to a newer mini. My MacBook Air (Mid 2011) is on it's last breaths as well so I'm trying to see which one's more urgent.
 

casperes1996

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Jan 26, 2014
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YMMV, but I have found when using Mojave with my Fusion Drive, since they were supported by APFS, has been lacklustre. Spinning beach balls from hell. Horribly slow. I do enjoy having the one large drive rather than split, but it's just painful. Shouldn't use APFS on rotational drives at all IMHO. I am in the process of deciding which SATA SSD to buy to replace the old internal platter portion of the Fusion.
Mojave works brillantly for me with my Fusion Drive. I have the 128GB SSD with 1TB hard drive from the first gen 5K iMac. The APFS volume is automatically modified when installed on a fusion drive, such that not all features of APFS are used on both drives, since some of the APFS functions split data apart, which doesn't matter so much on an SSD, but crushes performance on an HDD. APFS will try to avoid doing that on a spinner though, so it shouldn't be an issue
 

SketchyClown

macrumors member
Mojave works brillantly for me with my Fusion Drive. I have the 128GB SSD with 1TB hard drive from the first gen 5K iMac. The APFS volume is automatically modified when installed on a fusion drive, such that not all features of APFS are used on both drives, since some of the APFS functions split data apart, which doesn't matter so much on an SSD, but crushes performance on an HDD. APFS will try to avoid doing that on a spinner though, so it shouldn't be an issue
There is definitely something weird going on with APFS/Fusion. I have the 128GB SSD with the 2TB spinner and while things seemed snappy at first install, as a little time went on, the beachballs and just general sluggishness of the machine was pathetic.

Now I'm not entirely coming down on Mojave, as High Sierra with a HFS+ Fusion Drive wasn't a speed demon either, but it was noticeably more responsive than the APFS version.

My father's Late 2013 iMac is apparently working fine with Mojave + 3TB Fusion, and same with my brothers 2014 iMac. Both of them are "light duty users" who probably have 2.99TB free, so kinda hard to tell.
 

casperes1996

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Jan 26, 2014
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There is definitely something weird going on with APFS/Fusion. I have the 128GB SSD with the 2TB spinner and while things seemed snappy at first install, as a little time went on, the beachballs and just general sluggishness of the machine was pathetic.
How can we be sure your issues are APFS related though? There could be a multitude of reasons for your problems.

My father's Late 2013 iMac is apparently working fine with Mojave + 3TB Fusion, and same with my brothers 2014 iMac. Both of them are "light duty users" who probably have 2.99TB free, so kinda hard to tell.
As I said, it works brilliantly for me too, and I'm in no way a light user. I have about 100gigs free, I use the iMac for everything from video editing to software engineering and games. Entirely happy with the Fusion Drive, and actually can't remember the last time I beach-balled
 

SketchyClown

macrumors member
How can we be sure your issues are APFS related though? There could be a multitude of reasons for your problems.
Oh there *could* be. However, in testing, Mojave runs like a champ under APFS on the PCI-E SSD, but runs like a slug with the 2TB Fusion setup. High Sierra, on HFS+ also runs like a champ on straight SSD. Under the Fusion setup, it is nowhere near as slow as the Mojave APFS implementation, on my machine.

As I said, it works brilliantly for me too, and I'm in no way a light user. I have about 100gigs free, I use the iMac for everything from video editing to software engineering and games. Entirely happy with the Fusion Drive, and actually can't remember the last time I beach-balled
Glad to hear it's working for you. That, however doesn't equate to all others. But congrats. :)
 

casperes1996

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Jan 26, 2014
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Glad to hear it's working for you. That, however doesn't equate to all others. But congrats. :)
Of course not. Similarly however, your negative experience also doesn't equate to there being a general issue, so as it stands I'm not convinced either way. Neither that there is or isn't a performance issue
 

Mr. 123

macrumors regular
Sep 20, 2016
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How stable is Mojave by now? I am still running High Sierra on my 2017 iMac.
 

Fishrrman

macrumors P6
Feb 20, 2009
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My suggestion:

DON'T create a fusion drive.

Instead, use the SSD and the HDD as "standalone" drives.

The SSD will run better if left "as an SSD".
 

nkarafo

macrumors member
Oct 18, 2015
54
7
My suggestion:

DON'T create a fusion drive.

Instead, use the SSD and the HDD as "standalone" drives.

The SSD will run better if left "as an SSD".
I tried to install Mojave to imac 27" fusion drive but the ssd part of the disk (24gb) is not shown in installation. It's like hidden. Can I do something about it to install Mojave to SSD?
Thanks.
 

casperes1996

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Jan 26, 2014
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I tried to install Mojave to imac 27" fusion drive but the ssd part of the disk (24gb) is not shown in installation. It's like hidden. Can I do something about it to install Mojave to SSD?

If it's a Fusion Drive both the SSD and HDD will show as a single drive in the installer. Installing macOS onto a Fusion Drive will automatically install to the SSD
 
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