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WD unveils new high-capacity 32TB SMR and 26TB CMR disk drives
(www.techspot.com)
This is a most excellent place for technology news and articles.
2 parity is standard and should still be adequate. Likelihood of two failures within four days on the same array is small.
It's more likely if you bought all the drives from the same store (since that increases the likelihood that they're from the same batch), so you should make sure that you buy them from different stores.