To keep your data safe from any kind of failure, use the 3-2-1 backup rule. According to this rule, you need to keep three copies of your data, out of which two of them should be stored on two different kinds of storage. For instance, one could be an external drive and the other a NAS drive. And finally, you need to ensure that you keep at least one copy off-site so that another copy’s safe if there’s a disaster.