The replacement drives officially compatible with LaCie's 4big Quadra are no longer produced and/or expensive and/or defective: https://www.lacie.com/as/en/support/kb/lacie-big-products-drive-compatibility-list-007780en/
Could you whack any old drive in there, or is it not that simple?
Could you whack any old drive in there, or is it not that simple?