redis配置注意事项（适合于较大配置）

　　根据官方的建议，redis-server的相关配置建议如下，但是有些并不合适，LZ会进行说明（如果redis使用的内存还不到1GB，或者大量qps还不到1000的应用，这已经淘汰了99%的应用，很多配置基本上就无所谓了，基本上没这么大影响，保证高可用即可，不会有性能问题的；）：

1、vm.overcommit_memory = 1。实际中最好让redis主节点仅使用50-60%的内存，剩余的用于执行bgsave和创建写命令的缓冲区，保证最大可能的sla。

2、禁用linux内核特性transparent huge pages，echo never > /sys/kernel/mm/transparent_hugepage/enabled，oracle也如此要求，TPH和传统的大页在机制上有些不同，参见http://blog.itpub.net/26736162/viewspace-2214374/。

3、避免使用swap或禁用

4、设置maxmemory，限制redis使用的内存数量，而非自动，否则发生交换就奇慢无比了；

5、如果是ssd的话，复制模式下建议master节点启用持久化选项（当超过数GB时，保存快照会对前端影响较大，如果能够容忍极端情况下小部分更新丢失，应在slave节点机进行，而非master节点，主要可能是国外数据没国内这么大）；

6、一般应使用显示的redis.conf，而非使用内置的配置，可在启动时通过命令行指定/etc/redis.conf；

7、应显示设置rdb、aof日志文件目录及文件名，logfile参数；默认为工作目录：

# The filename where to dump the DB
dbfilename dump.rdb   # rdb文件名

# 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.    # rdb存储目录
dir ./

[root@XXX redis-3.2.12]# ll | grep dump
-rw-r--r--  1 root root  19274 Aug  8 20:12 dump_16379.rdb
-rw-r--r--  1 root root   1259 Aug  8 22:23 dump_46379.rdb
-rw-r--r--  1 root root 446620 Nov 23 02:05 dump.rdb

############################## 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 yes

# The name of the append only file (default: "appendonly.aof")

appendfilename "appendonly.aof"

# 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   AOF默认每秒写一次，跟mysql的innodb redo刷新机制是一样的
appendfsync everysec
# appendfsync no

8、各个版本的详细配置可参考：

9、重要的是：

1、单进程架构，这意味着单个key的value不能过大，例如几兆，这会严重影响TPS，具体拆分可以参考：https://blog.csdn.net/beyond59241/article/details/78889867/
2、支持多database，不过最好使用多个instance的方式，有些客户端可能不支持多instance，同时性能也比较难以排查
3、不支持namespace的概念，所以最好使用前提前规划，比如namespace:key_name的方式，避免日后混乱
4、vm.swappiness=0 在os swap期间，进程会block直到完成，所以应该尽量避免

10、客户端缓冲大小配置，尤其是是在行情接收场景中。https://blog.csdn.net/luyaoying001/article/details/80264347

11、其它实践可以参考：https://www.cnblogs.com/ajianbeyourself/p/4472788.html

12、避免快照所在盘磁盘空间满，否则容易出现redis挂起。