Principles, advantages and disadvantages of two persistence mechanisms RDB and AOF of redis

Here is Redis The advantages and disadvantages of the two persistence mechanisms are also very important ：

Redis Based on Key-Value Structure of the memory database ,Redis for fear of Redis A problem of data loss caused by failure provides RDB and AOF Two persistence mechanisms

• RDB The persistence mechanism is implemented through snapshots , In other words, according to a trigger condition of the snapshot, the data snapshot in memory will be written to the disk and stored in the form of binary compressed files RDB There are many snapshot methods as follows ：
  • perform bgsave Command triggers an asynchronous snapshot , perform save Command triggers a synchronized snapshot , The difference between the two ： Synchronizing snapshots can block the client's execution instructions
  • according to redis.conf The configuration in the file , Automatic triggering bgsave
  • The master-slave copy will trigger

• AOF Persistence is a near real-time approach , hold Redis Server Execute the transaction command for additional storage , That is, the customer is performing a data change operation ,Redis Such a command will be appended to aof In the buffer of , Then write the data in the buffer to the disk aof In the document , When finally Really persistent data to disk aof In the document , It is determined according to the disk brushing strategy , in addition AOF A way of appending this instruction will cause AOOF Too large file brings obvious IO Performance issues , therefore Redis For such a situation, it provides AOF Rewrite mechanism , When AOF When the file size reaches a certain value, the same instructions in the file will be compressed

 

RDB and AOF Advantages and disadvantages ：

1. RDB Is to trigger persistence at regular intervals , Therefore, the data security is low ,AOF It can achieve real-time persistence , Data security is high
2. RDB Files are persisted by compression by default ,AOF Stored are execution instructions , therefore RDB Performance ratio during data recovery AOF It is better to

The advantages and disadvantages also depend on the current specific application scenarios ！！！！