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golfgirlgolf

macrumors regular
Original poster
I just purchased a 6 month old iMac and found the previous user/seller has done something goofy with the formatting of the Fusion drive. Now there are two volumes on the desktop and in Disk Utility. The SSD and HDD.

I'd like to restore it to the factory setup. (One volume for everything SSD+HDD combined) There's no worry about backing up anything the machine is blank. Unfortunately all recovery modes/Disk Utility don't see the problem - DU doesn't think it needs fixing!

But at the same time I'm wondering what's the difference? Why not just put programs on the SSD and data on the HDD? It would be a PITA for backups though.

Any ideas how to easily re-pair the SSD and HDD back up again as it was shipped?

This is a late 2015 Retina iMac and from what I've read El Capitan (default OSX) had removed the Fusion pairing function out of Disk Utility.
 

Taz Mangus

macrumors 604
Mar 10, 2011
7,815
3,504
I just purchased a 6 month old iMac and found the previous user/seller has done something goofy with the formatting of the Fusion drive. Now there are two volumes on the desktop and in Disk Utility. The SSD and HDD.

I'd like to restore it to the factory setup. (One volume for everything SSD+HDD combined) There's no worry about backing up anything the machine is blank. Unfortunately all recovery modes/Disk Utility don't see the problem - DU doesn't think it needs fixing!

But at the same time I'm wondering what's the difference? Why not just put programs on the SSD and data on the HDD? It would be a PITA for backups though.

Any ideas how to easily re-pair the SSD and HDD back up again as it was shipped?

This is a late 2015 Retina iMac and from what I've read El Capitan (default OSX) had removed the Fusion pairing function out of Disk Utility.

You first need to create a bootable OS X installer: http://www.macworld.com/article/298...le-os-x-10-11-el-capitan-installer-drive.html.

Next boot to the installer that you created by holding down the option-key while rebooting and select the bootable installer.

On the top menu bar select Utilities then Disk Utility. In Disk Utility erase both the SSD and the spinning HD. Exit Disk Utility.

Open Terminal next from the Utilities and follow this: http://www.techrepublic.com/article/pro-tip-how-to-create-and-disable-a-fusion-drive/.

Once that is complete, exit Terminal and go install OS X.
 
Last edited:

Fishrrman

macrumors Penryn
Feb 20, 2009
28,967
13,015
Is the iMac a "1tb fusion" model, or a "2tb fusion" model?
The 1tb model has only a 24gb SSD. The 2tb model has a 128gb SSD.

If you always want the fastest possible performance from the SSD, leave the "2 drive setup" as it is.

Put the OS, apps, accounts onto the SSD.
Keep "large libraries" (pics, music, movies) on the HDD.

This way, you can keep the SSD "lean, clean and mean". It won't get clogged up as fusion shuffles things around to it and from it (from the HDD).

Of course, you will have TWO icons to manage on the desktop.
So what?
I keep no less than 7 or 8 volume icons mounted on my desktop at all times.

Backup will be just as easy.
I use CarbonCopyCloner to clone all my individual volumes/partitions to backups.
Nuthin' to it.
 

Taz Mangus

macrumors 604
Mar 10, 2011
7,815
3,504
Is the iMac a "1tb fusion" model, or a "2tb fusion" model?
The 1tb model has only a 24gb SSD. The 2tb model has a 128gb SSD.

If you always want the fastest possible performance from the SSD, leave the "2 drive setup" as it is.

Put the OS, apps, accounts onto the SSD.
Keep "large libraries" (pics, music, movies) on the HDD.

This way, you can keep the SSD "lean, clean and mean". It won't get clogged up as fusion shuffles things around to it and from it (from the HDD).

Of course, you will have TWO icons to manage on the desktop.
So what?
I keep no less than 7 or 8 volume icons mounted on my desktop at all times.

Backup will be just as easy.
I use CarbonCopyCloner to clone all my individual volumes/partitions to backups.
Nuthin' to it.

That is exactly what I would do, OS on SSD and user accounts on the spinning HD. The other nice thing about having them separated is makes it easier if you need to do a clean install of the OS, user accounts don't get affected by that.
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Thanks -

I'm surprised someone hasn't written a program to automate this from a bootable drive - select the 2 drives and hit GO. In any event I got through it all and it worked!

Glad it worked for you. Most people would not bother to un-Fusion the hard drive, so it is probably not worth the effort to automate what you suggest.
 
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