[waterhouse]

This is a good thing to do.

For higher-hanging fruit, if you don't have enough different models of drives to make them all unique, then you might still try to protect against a run of manufacturing defects. Suppose there was a slightly defective machine making a series of drives with a certain problem. If you do things like buy drives in different groups from different middlemen or at different times, and either take one from each group or put them into a big pool and grab them at random, then that decreases the likelihood of having multiple drives from a single defective run end up in the same array.