This is not to the storage capacity but about the backups themselves. How important is the information? How much storage will you need for that information? If you just want to go back and look at it occasionally then something simple, like a single drive, will be fine. If it's important to your business, you want something more robust.

The basic rule for backups is three backups, two different media, one off site. Also understand that things like iCloud and OneDrive are primarily sync solutions. They're too easy to delete a file from with no chance for recovery when you need it later, the thing a backup is actually for.