Obviously this is a software problem, an incompatibility with SoftRAID and Mojave, that will probably never be found, but I thought I might as well report it anyway.

The restore is chugging right along and the utility shows no errors on any drive or on either RAID volume. I am now a couple of hours into the all-night process of restoring from the backups. With multiple RAID options, you decide what you’re using your RAID volume for and how much space to allocate. SoftRAID easy setup makes it a breeze to create RAID volumes by helping you through the entire process. Now you can quickly access and robustly protect your data with SoftRAID XT. Since I have both RAID volumes (mostly) backed up, I decided what the hell, and used SoftRAID 5.7.2 to destroy the RAID by initializing all 4 drives, and then rebuilt the RAID and both of its partitions in exactly the same configuration as before, but now of course empty. Includes SoftRAID: Easy and Complete Drive Management. The Mac OS disk utility would successfully run First Aid on BOTH RAID partitions, but would never mount one of them, and the SoftRAID utility would always say 'waiting for mount'. Same thing, the rebuild would get to a certain point and then hang, and the volume would refuse to mount. I put in an identical spare 8TB drive and started a rebuild. I took the 'bad' drive out and reseated it. It was simply too much of a coincidence that the drive would just happen to go bad during the OS upgrade. The SoftRAID 5.7.2 application said something about an I/O error on one of the four drives, but also said that drive's SMART status was OK and on another line said '0 errors'. Both should have mounted automatically and always did before.

In the morning, one of my two RAID 5 volumes was mounted grayed-out with a red exclamation point, and the other was not mounted at all. I've been waiting to upgrade to Mojave and for some idiotic reason I did so a couple of nights ago. Again, I had never experienced any issue with my RAID. The raid was (obviously) a 24TB raid drive but I divided it into two 12TB volumes, both of which mounted automatically. The machine is a 2018 iMac 27' Retina with 64gb memory. I have been running a Thunderbay 4 on Thunderbolt 3 with 4 8TB seagate ironwolf drives in RAID 5 under High Sierra (SoftRAID XT 5.7 and 5.7.2) for months with no problems of any kind.

Softraid 6 xt