A common system task is backing up files – that is, copying files with the ability to go back in time and restore them. For example, if someone erases or overwrites a file but needs the original version, then a backup allows you to go back to a previous version of the file and restore it. In a similar case, if someone is editing code and discovers they need to go back to a version of the program from four days earlier, a backup allows you to do so. The important thing to remember is that backups are all about copies of the data at a certain point in time.

In contrast to backing up is “replication.” A replica is simply a copy of the data when the replication took place. Replication by itself does not allow you to go back in time to retrieve an earlier version of a file. However, if you have a number of replicas of your data created over time, you can sort of go back and retrieve an earlier version of a file, but you need to know when the replica was made, then you can copy the file from that replica.