本文主要是对于redis安装与持久化中非常浅显的知识进行介绍，并不深入了解，只接触表面，对一些较复杂的内容也不过多描述。如文中有错误之处，望不吝赐教，谢谢~
一、Redis简介
Redis（Remote Dictionary Server )，即远程字典服务，是一个开源的使用ANSI C语言编写、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API。
Redis是一款高性能的NOSQL系列的非关系型数据库,redis在Java开发中主要用来存储缓存用的数据以及在需要高速读/写的场合使用它快速读/写。
NoSQL技术，这是一种基于内存的数据库，并且提供一定的持久化功能。
Redis和MongoDB是当前使用最广泛的NoSQL，而就Redis技术而言，它的性能十分优越，可以支持每秒十几万此的读/写操作，其性能远超数据库，并且还支持集群、分布式、主从同步等配置，十分强大。
在一般情况下，不区分redis技术和redis数据库，都称作redis。
redis作为一种非关系型数据库，其是基于内存，不同于关系数据库基于硬盘，其速度远远大于关系数据库。但是由于内存的局限性，所以对何种数据何时使用redis我们需要做出取舍。
一般对于读操作较多且数据量较小的情况可考虑使用redis，例如“好友列表查询”“排行榜”等等。
二、安装redis
（1）进入github-redis下载redis压缩包
（2）解压下载下来的redis-64-3.0.503.zip ,直接打开便可使用。（其实这是绿色版本，不用安装，下载下来解压就好）。
- redis.windows.conf：配置文件
- redis-cli.exe：redis的客户端
- redis-server.exe：redis服务器端
一般启动好服务器端再打开客户端就可以使用redis了。
三、redis持久化
由于redis的数据存储在内存中，不便于保存（当服务器和客户端关闭或电脑关机时，数据会丢失），为了将redis中的数据保存在硬盘中，便需要持久化技术。
redis持久化分为两种方式一种是RDB（默认方式），一种是AOF方式。
（1）RDB
在redis.windows.conf配置文件中，有专门对RDB持久化的配置。
################################ 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 completely by commenting out all "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
*“sava 900 1”*表示900秒内至少有一个键值发生改变，就执行持久化操作一次,相应的我们可以根据需要自行修改持久化条件。
每次持久化后的rdb文件会保存在redis的解压目录下。
（2）AOF：日志记录的方式，可以记录每一次命令的操作并持久化
在redis.windows.conf配置文件中，有专门对AOF持久化的配置。
############################## APPEND ONLY MODE ###############################
# By default Redis asynchronously dumps the dataset on disk. This mode is
# good enough in many applications, but an issue with the Redis process or
# a power outage may result into a few minutes of writes lost (depending on
# the configured save points).
#
# The Append Only File is an alternative persistence mode that provides
# much better durability. For instance using the default data fsync policy
# (see later in the config file) Redis can lose just one second of writes in a
# dramatic event like a server power outage, or a single write if something
# wrong with the Redis process itself happens, but the operating system is
# still running correctly.
#
# AOF and RDB persistence can be enabled at the same time without problems.
# If the AOF is enabled on startup Redis will load the AOF, that is the file
# with the better durability guarantees.
#
# Please check http://redis.io/topics/persistence for more information.
appendonly no
"appendonly no"表示默认AOF方式是关闭的，若要打开，将no改为yes即可。
# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting for more data in the output buffer. Some OS will really flush
# data on disk, some other OS will just try to do it ASAP.
#
# Redis supports three different modes:
#
# no: don't fsync, just let the OS flush the data when it wants. Faster.
# always: fsync after every write to the append only log . Slow, Safest.
# everysec: fsync only one time every second. Compromise.
#
# The default is "everysec", as that's usually the right compromise between
# speed and data safety. It's up to you to understand if you can relax this to
# "no" that will let the operating system flush the output buffer when
# it wants, for better performances (but if you can live with the idea of
# some data loss consider the default persistence mode that's snapshotting),
# or on the contrary, use "always" that's very slow but a bit safer than
# everysec.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use "everysec".
# appendfsync always
appendfsync everysec
# appendfsync no
"appendfsync always"表示每一次操作都进行持久化，“appendfsync everysec”表示每隔一秒进行一次持久化操作（默认是这样），“appendfsync no”表示不进行持久化操作。
每次持久化后的aof文件会保存在redis的解压目录下。
2020.03.07
