It depends on your needs. How much do you value your data? Can you re-create / re-download it in case of a disk failure?
In some case, like a typical home users with a few writes per day or even week simply having a second disk that is updated every day with rsync may be a better choice. Consider that if you’re two mechanical disks spinning 24h7 they’ll most likely fail at the same time (or during a RAID rebuild) and you’ll end up loosing all your data. Simply having one active disk (shared on the network and spinning) and the other spun down and only turned on once a day with a cron rsync job mean your second disk will last a LOT longer and you’ll be safer.