Does Redis persist data?

Redis supports so-called “snapshots”. This means that it will do a complete copy of whats in memory at some points in time (e.g. every full hour). When you lose power between two snapshots, you will lose the data from the time between the last snapshot and the crash (doesn’t have to be a power outage..). Redis trades data safety versus performance, like most NoSQL-DBs do.

Redis saves data in one of the following cases:

• automatically from time to time
• when you manually call BGSAVE command
• when redis is shutting down

But data in redis is not really persistent, because:

• crash of redis process means losing all changes since last save
• BGSAVE operation can only be performed if you have enough free RAM (the amount of extra RAM is equal to the size of redis DB)