I have been updating the vdevs in my pool snice the average age of the old 4tb drives is over 60,000 hours. With the typical old drive being something that I shucked or bought anywhere I could find a 4tb. Performance has always been great. The only reason I am replacing is due to age.

So far after replacing one of those vdevs with 12tb WD Reds, I noticed a major temp spike of a couple of degrees C. As a result I turned up the cooling to address it.