Redis持久化功能
Redis为了内部数据的安全考虑，会把本身的数据以文件形式保存到硬盘中一份，在服务器重启之后会自动把硬盘的数据恢复到内存(redis)的里边。
数据保存到硬盘的过程就称为“持久化”效果。
1. snap shotting快照持久化
该持久化默认开启，一次性把redis中全部的数据保存一份存储在硬盘中，如果数据非常多(10-20G)就不适合频繁进行该持久化操作。
下方是快照持久化在本地硬盘保留的数据备份文件（redis自动生成）：
查看快照持久化的备份频率（打开redis.conf）：
- ################################ SNAPSHOTTING #################################
- #
- # Save the DB on disk:
- #
- # save <seconds> <changes>
- #
- # Will save the DB if both the given number of seconds and the given
- # number of write operations against the DB occurred.
- #
- # In the example below the behaviour will be to save:
- # after 900 sec (15 min) if at least 1 key changed
- # after 300 sec (5 min) if at least 10 keys changed
- # after 60 sec if at least 10000 keys changed
- #
- # Note: you can disable saving at all commenting all the "save" lines.
- #
- # It is also possible to remove all the previously configured save
- # points by adding a save directive with a single empty string argument
- # like in the following example:
- #
- # save ""
- save 900 1
- save 300 10
- save 60 10000
save 900 1 #900 秒内如果超过 1 个 key 被修改，则发起快照保存
save 300 10 #300秒超过10个key被修改，发起快照
save 60 10000 #60秒超过10000个key被修改，发起快照
以上三个save的理解：
数据修改的频率非常高，备份的频率也高
数据修改的频率低，备份的频率也低
查看快照持久化文件的名字和存储位置（打开redis.conf）：
- # The filename where to dump the DB
- dbfilename dump.rdb
- # The working directory.
- #
- # The DB will be written inside this directory, with the filename specified
- # above using the 'dbfilename' configuration directive.
- #
- # The Append Only File will also be created inside this directory.
- #
- # Note that you must specify a directory here, not a file name.
- dir ./
快照持久化 和 精细持久化 可以尽最大程度保证数据的安全：
2、手动发起快照持久化
手动发起快照持久化
