Additional comments:
-RAID1 performance is virtually identical to that of a single drive setup. Thousands of benchmarks online will support that fact so I am not going to post an arbitraty one here but think about it: all it does is the raid controller mirrors to the second drive whatever is done on the first drive. That second drive doesn’t impact performance at all.
-the VMs caused such disk issues because they had lots of small disk writes… write performance of small files of RAID 5 is its achilles heel, so that likely will account for the issue there.