I have just updated to 6.0 update1 (build 3073146) using the HP image so we'll see how it goes. I will update this thread.
It looks promising because before this I noticed that my Performance Chart for Disk had non-stop activity on it, even though I had no guest VMs running. Now I only see minimum activity on the Disk chart. Interesting.
Yes, I do have a spare drive configured in the Raid5 config of the p410i. If the update above doesn't solve the issue, my next action will be to remove the spare as some have suggested.