Add 3rd disk to rai...
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Add 3rd disk to raid 1 array

New Member

I have a raid 1 array with 2 x 4tb disks

Each disk is partitioned into 2 volumes.

1 volume is being used for time machine, the other for sundry precious files.

I want to add a 3rd 4TB disk for offsite backup.

Where do I look for step by step instructions?

Topic starter Posted : 11/06/2021 2:15 am
Member Admin

Its slightly harder with two disks, but here are simplified steps:

Unmount the two volumes from the desktop (command e, or drag to trash)

You may have to force eject the Time machine volume.

Run SoftRAID

Initialize the new disk.

Click on one of the volumes and "Add disk" , or "add secondary disk in SoftRAID. Let it rebuild.

Unmount the two voumes from the desktop (command e, or drag to trash)

Click on the other volume and "Add disk", or "add secondary disk in SoftRAID

Let it rebuild.


Hopefully all will be simple, good luck!


Posted : 11/06/2021 10:05 am
New Member

thank you for your prompt reply.

Before adding the 3rd disk to my raid 1 array i received errors on one of the 2 disks already installed

So i replaced it.

Certified the new disk (Red Primary plus)

added it to the original (Red secondary)

The sundry volume works fine.

the time machine volume won't mount

something to do with HFS+ v APFS formatting?

running BigSur 11.4

Cheers, Dave

Topic starter Posted : 14/06/2021 6:18 pm
Member Admin


In Big Sur, time machine volumes must be APFS. You can use a beta version of SoftRAID tocreate an APFS volume, but you d not need to install the driver or use the beta after creating the volume.

Posted : 15/06/2021 1:40 am
New Member


I understand that now.

It is curious that the volume continued to mount and work with time machine up until I rebuilt the volume.

Now my problem is how to reformat the volumes to APFS without losing my backups.

Screen Shot 2021 06 15 at 4.20.35 pm


Topic starter Posted : 15/06/2021 1:54 am
New Member

@softraid-support I have given up on this project after discovering I cannot transfer my time machine backups from HFS+ to APSF

Even If I could resurrect them from my damaged set.

I have been able to retrieve my sundry files.

My next project will be to rebuild the 2 volumes as APSF and see if I can get the time machine running again. (anew)

Topic starter Posted : 15/06/2021 3:45 am
Member Admin


I think the rebuild must have triggered Time Machine to sense a "Change" in the volume. Speculating.

Sorry you have to start over. I think everyone with both Apple RAID or SoftRAID Time Machine volumes will have the same issue. Apple just migrated backups to APFS.

Its possible down the road we may be able to convert HFS to APFS.

Posted : 15/06/2021 12:35 pm