Redis has two persistence mechanisms: RDB (Redis Database) and AOF (Append-Only File).
1. RDB (Redis Database) persistence mechanism
RDB is the default persistence method of Redis, which saves the data state of Redis at a certain point in time to a binary file on disk. This file is a snapshot (snapshot), which contains all the contents of Redis data at a specific moment, including key-value pairs, data types, etc. RDB persistence is an operation that is performed periodically, and the administrator can set the frequency of RDB persistence through configuration.
advantage:
·High efficiency: Since RDB is a snapshot file, its recovery speed is very fast, which is suitable for large-scale data recovery.
· Small footprint: RDB file is a compact binary file, suitable for backup and data migration.
Relatively small impact on performance: Since RDB is persisted in the background, it has little impact on the performance of the Redis server.
shortcoming:
Possible data loss: Since RDB is executed periodically, if Redis fails after the last persistence, some data may be lost.
Not suitable for scenarios with high real-time data requirements: RDB persistence is periodic. If the Redis server fails before persistence, the data from the last persistence to the time of failure will be lost.
2. AOF (Append-Only File) persistence mechanism
AOF persistence is to append Redis operation commands to the file, and it records all write commands received by the Redis server in text form. This means that the AOF file contains all the operations of rebuilding the dataset, so as to achieve data persistence. AOF persistence can also be configured to set the frequency of saving data.
advantage:
Better data protection: AOF persistence is more secure than RDB, because it records all write operation commands. When Redis restarts, the data can be recovered by re-executing these write operation commands.
Higher real-time data: The frequency of AOF persistence can be configured according to requirements, which can achieve higher frequency persistence and reduce the risk of data loss.
shortcoming:
Larger files: Since AOF files are text files and will record all write operation commands, compared with RDB files, AOF files are usually larger, which may increase the occupation of disk space.
Relatively slow restore: Restoring an AOF file is usually slower than loading an RDB file because it requires re-executing all write commands.
When choosing a persistence mechanism, it needs to be decided according to specific application scenarios and requirements. Usually, RDB and AOF can be used in combination to balance data recovery speed and data protection. For example, AOF persistence can be used to record all write operations in real time, and RDB persistence can be used to periodically create snapshots to back up data. This can reduce the overhead during recovery while ensuring data security.