In Running Nextcloud on Raspberry PI next steps I discussed adding a external drive with ZFS. But I only used a single drive, if that was the end game I would have been much better off sticking wtih EXT4 or similar. Well now I am going to take advantage of ZFS and add a second drive.
I picked up a second drive identical to the first. With this I plan to set up a mirror of the first drive so that if one drive dies, then I won't lose any data. Importantly this will also add some protections on more subtle data corruption that I may not notice.