Adding a HDD to SSD PCI flash based mac mini late 2014

I managed to add the second SSD using the iFixit kit and teardown (great product/pictures).

I have an issue with the fusion. Even though the mini is SSD-PCIe only, there is an existing CoreStorage volume. I don't think I can add a second HD to an exisiting corestorage. Do I need to delete it and create a new one from scratch?

Or is it best to reinstall from the recovery and overwrite with my latest time-machine backup?

Thanks for any support :-)

Opps! You can't create a Fusion Drive set with two SSD's! But you can run them independently.

The rub here is how the OS see's the drives. Think of it this way I have a Red (HD) drive and a Blue (SSD) drive each is weighted differently within the OS (HD Vs SSD).

Now instead of having two distinct drives think of having two Blue drives! Which Blue drive is the base drive?? No, its that Blue drive, No! It's that Blue ;-}

You'll end up having a mess! This is only an issue within the system. You can create RAID sets with external drives as they use their own drivers.

No worries. I have another HDD, I thought I'd be clever! MacOSX doesn't add the HDD to existing corestorage volume (must be factory installed on PCi SSD-only as I didn't make it). Can't find a way to add HDD to the volume, so is it best delete the corestorage volume and recreate from scratch? Thanks!

$ diskutil coreStorage list

CoreStorage logical volume groups (1 found)

+-- Logical Volume Group 88E23BEE-0320-4FCF-B327-9ED9A8F3E5E8

Name: Macintosh HD

Status: Online

Size: 250139852800 B (250.1 GB)

Free Space: 8921088 B (8.9 MB)

+-< Physical Volume 550E2DD7-00ED-4A0E-B16A-E43EED6E72E3

| Index: 0

| Disk: disk0s2

| Size: 250139852800 B (250.1 GB)

+-> Logical Volume Family 1B0792DB-B6CF-4CFA-BD5F-63C70C2A10F5

Encryption Type: None

+-> Logical Volume A7E18B5C-8852-4B06-B4DC-B7C8E38C2010

Disk: disk2

etc.

HDD is on /dev/disk1

In the end I resolved my issue so I'm updating this post for others.

(1) ensure an additional complete backup on Time Machine

(2) Reverted the CoreStorage volume instead of deletion (https://support.symantec.com/en_US/artic...)

(3) create the fusion drive per instructions in the above post (http://www.techrepublic.com/article/pro-...). In my case I did not build a fusion drive with the full disks (i.e. /dev/disk0 and /dev/disk1), I selected the specific partitions hoping to preserve EFI and recovery partitions. In my case, it meant pointing to /dev/disk0s2 and /dev/disk1s2

(4) Reinstall the fusion drive from the time machine backup.

This was done on 10.12.2 before updating to 10.12.3. 10.12.3 did not break my fusion drive