Disk being utilized by another program
I'm trying to do a 4 bay drive into Raid 0 but when I initialize it states one of the drives, which is the older drive, is being used by another program and that I should shut down the program but the drive is formatted to APFS. Do I need to reformat this drive again? It doesn't allow me to do "zero" since it's currently being used by another program.
Make sure all volumes on the disk are unmounted. Then try again. SoftRAID first must unmount the volume and if it won't unmount, you will get this message.
You can use lsof piped to grep /Volumes/VOLUMENAME to see which processes are using the drive.
I had this difficulty a short time ago; it turned out that mds (spotlight) and notifyd were using the drive. I was able to use
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
to convince spotlight to give up on the disk (caution: effectively turns off spotlight indexing for all drives), but I did not figure out how to prod notifyd, so I ended up using the "force eject"