I have a RAID0 volume that was created on an OWC ThunderBlade disk on a computer running Big Sur (Mac Pro, which I no longer have access to).
I am now trying to delete that volume on a MacBook Pro M1 Max running Monterey 12.3.1 (SoftRAID version is 6.2.1) but it keeps saying that the disk is currently in use and won't let me delete it. I've tried closing all other applications and rebooting but keep getting the same error.
More likely the problem is the SoftRAID driver is not loaded.
Did you do this?
https://support.apple.com/en-lk/guide/mac-help/mchl768f7291/mac
Select reduced security and enable this:
Select the “Allow user management of kernel extensions from identified developers” checkbox to allow installation of software that uses legacy kernel extensions.
Now you need to reinstall the SoftRAID driver.
After enabling third party extensions, reinstall the SoftRAID driver, (do not immediately restart) and go to System Preferences / Security to "Allow" OWC as an identified developer.
Also, you should navigate to System Preferences/Security/Privacy/Full Disk Access and enable full disk access for SoftRAID.
@softraid-support I had already enabled reduced security and installed the SoftRAID driver and used SoftRAID to delete/create another RAID volume on a different device.
One thing I hadn't done was enable full disk access for SoftRAID, but even after doing that I wasn't able to delete the volume on the ThunderBlade.
I can't unmount it because the Thunderblade is showing as unmounted in SoftRAID even though it is mounted (I can access the files on it).
You need to attach a SoftRAID tech support file, so I can take a closer look.
It looks like maybe you initialized it as APFS inside Disk Utility? there is an APFS volume inside the HFS container.
See if you can erase it again, in Disk utility (as HFS)
If not, "uninstall SoftRAID driver".
restart
Run Disk utility and erase the 4 disks. (HFS)
quit and run SoftRAID, install the driver, "Allow" OWC and restart once more. Then you can go forward from there.

