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GregorMae

macrumors newbie
Original poster
Nov 5, 2018
11
1
Europe
Hello!

Yesterday I bought the iMac 5K with 3TB Fusion drive. I've made two partitions - one for storage (2,5 TB) and one for the system (512 GB). Because I bought the iMac second hand I've clean installed the MojaveOS with the APFS file system. The other partition is Mac OS Extender (Journaled).

Because of the "container" disk shown in the attached screenshot, that wasn't there before I've formatted the disk I'm now not sure if the Fusion drive is working properly.

eTZQSbl.png


LuAro41.png


How can I check if everything is working optimally?

Thanks in advance!

Best,
Gregor
 

chrfr

macrumors G5
Jul 11, 2009
13,729
7,306
Hello!

Yesterday I bought the iMac 5K with 3TB Fusion drive. I've made two partitions - one for storage (2,5 TB) and one for the system (512 GB). Because I bought the iMac second hand I've clean installed the MojaveOS with the APFS file system. The other partition is Mac OS Extender (Journaled).

Because of the "container" disk shown in the attached screenshot, that wasn't there before I've formatted the disk I'm now not sure if the Fusion drive is working properly.

How can I check if everything is working optimally?

Thanks in advance!

Best,
Gregor
I would avoid partitioning the disk. There's no performance gain to be had by doing it, and you're likely to prevent the Fusion Drive from working as intended.
 

GregorMae

macrumors newbie
Original poster
Nov 5, 2018
11
1
Europe
I would avoid partitioning the disk. There's no performance gain to be had by doing it, and you're likely to prevent the Fusion Drive from working as intended.
I don't understand why I wouldn't - I like to keep my data organised in this case on two separated partitions.
  • You can use Disk Utility to add a single macOS partition to the hard disk on Fusion Drive, and that partition will function as a separate volume, not as part of Fusion Drive. Disk Utility then dims the
    IL_AddButtonMail.png
    button to prevent additional partitions. If creating a Windows partition, use Boot Camp Assistant instead.
https://support.apple.com/en-jo/HT202574
 

Fishrrman

macrumors Penryn
Feb 20, 2009
29,279
13,378
OP:

If you want to partition your drive, well... just do it.
I do the same, and don't worry what others may think.

Having said that, I remember a story about someone asking a German automobile engine designer about tachometers.
The designer replied, "why do you need a tachometer? The engine is either running, or it isn't".

Told you that to tell you this:
If your newly-partitioned drive checks out ok using Disk Utility's "repair disk" feature, what else is there to know, really?
The drive is either "running", or it isn't....! ;)
 
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Brian33

macrumors 65816
Apr 30, 2008
1,474
372
USA (Virginia)
You can verify that a Fusion drive is working properly by using Terminal commands. (At least with HFS+, I haven't tried with APFS-formatted volumes.)

First you need to use "diskutil list" and figure out the system-assigned names for the physical drives that make up the "fusion drive"; one being the solid-state drive and one hard disk drive.

Then you can use the Terminal command "iostat -d -w 1" to display the second-by-second disk activity. While that's going, copy or create a new file bigger than 4 GB. (On my system at least, the fusion set-up keeps about 4 GB of space free on the solid-state portion; we want to fill that up and then continue writing to the hdd.)

During the file write, you should see lots of io activity, first on the solid-state device (until its "fusion buffer" is used up), and then on the associated hdd device.

I've verified my own do-it-yourself Fusion drive this way.
 
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