I have an 8TB hard drive in my desktop, and another in a low power server in my detached garage. They automatically synchronize via syncthing. Every year or two

I have an 8TB hard drive in my desktop, and another in a low power server in my detached garage. They automatically synchronize via syncthing. Every year or two I'll make a cold backup to a 3rd drive. This has the benefit of making sure all the data is read periodically.