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This article mainly introduces the differences between the two persistence methods of redis. It is very detailed and has a certain reference value. Friends who are interested must read it!

Redis provides two ways for persistence, one is RDB persistence (the principle is to dump the database records of Reids in memory regularly to RDB persistence on disk), and the other is AOF (append only file) persistence (the principle is to write the operation log of Reids to a file in an appended way).

RDB persistence means that the snapshot of the dataset in memory is written to disk within a specified time interval. The actual operation is a child process of fork, which first writes the dataset to a temporary file, and then replaces the previous file and stores it with binary compression.

AOF persistence records every write and delete operation processed by the server in the form of log, query operation is not recorded, it is recorded in the form of text, and you can open the file to see the detailed operation record.

The difference between RDB persistence and AOF persistence:

1. Store data

RDB persists all key-value pairs in the key space (including the data in the expired dictionary) and saves them in binary form, which conforms to the rdb file specification and will be handled differently according to different data types.

AOF persists all write commands executed by the redis server to record the database state, and the commands are stored in the aof_buf buffer before writing.

2. Persistence time selection

RDB persistence sets the persistence behavior (number of modifications per unit time) through the save option of conf.

AOF persistence sets the persistence behavior (number of modifications per unit time) through the appendfsync option of conf.

3. Data restore

RDB persistence: the server loads the rdb file, blocks the thread, and does not accept any commands until the load is complete.

AOF persistence: the server creates a pseudo client without a network connection, reads all commands in the aof file and executes (redis service enables aof persistence, the aof file is selected to restore the database state when the server starts)

4. Expired key

RDB persistence ignores expired keys when writing or reading

AOF persistence does not ignore expired keys and appends a delete command to the aof file when the key is deleted lazily or periodically

5. File size

RDB persistence varies with the amount of data stored (data compression optimizations vary according to different data types)

AOF persistence increases as commands are executed (optimized by aof rewriting)

These are all the contents of the difference between the two persistence methods of redis. Thank you for your reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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