Redis Persistence

Redis provides the ability to persist data to disk, ensuring that the data is not lost even if the Redis server restarts. This is accomplished through Redis persistence options, which include RDB snapshotting and Append-only file (AOF).

RDB Snapshotting

RDB snapshotting is the default persistence mechanism in Redis. It creates a point-in-time snapshot of the dataset by dumping the Redis database into an RDB file. The RDB file is a binary file that contains all the Redis keys and their associated data.

To configure RDB snapshotting, you can modify the redis.conf file or use the CONFIG command at runtime. By default, RDB snapshotting is enabled, and Redis saves the dataset to disk automatically every 60 seconds if at least one key has changed.

Append-only File (AOF)

The AOF persistence mechanism allows Redis to log every write operation to a file. The AOF file stores a log of all the write operations executed by Redis, which can be used to reconstruct the dataset on server restart. By default, AOF persistence is disabled, but it can be enabled by modifying the redis.conf file or using the CONFIG command at runtime.

To ensure data durability, Redis supports different AOF writing modes: always, everysec, and no. The always mode synchronously writes every write operation to the AOF file, providing high data durability but lower performance. The everysec mode asynchronously writes the log file to disk every second, striking a balance between data durability and performance. The no mode relies on the operating system's cache and is the fastest option but carries the risk of data loss in the event of a server crash.

Here's an example of how to configure Redis to enable AOF persistence using the redis.conf file:

1# Enable AOF persistence
2appendonly yes
3
4# Set AOF writing mode to every second
5appendfsync everysec