At this size, the rebuild time is a day, or even 2-3 days if it's actively being used during the rebuild. It still makes sense to do at least a 2x raid1, which

At this size, the rebuild time is a day, or even 2-3 days if it's actively being used during the rebuild. It still makes sense to do at least a 2x raid1, which rebuilds faster than a cluster over wired ethernet. But if you have this much online storage, you probably have a high availability need also, which implies cluster in case a storage brick loses a power supply or logic board. It's not just a drive that can fail.