redis 的備份策略，最好使用：RDB-AOF 混合持久化

相關資料：

1. Redis 4.0 新功能簡介：RDB-AOF 混合持久化：http://blog.huangz.me/2017/redis-rdb-aof-mixed-persistence.html
2. 持久化（persistence）：http://redisdoc.com/topic/persistence.html?highlight=持久化

• 下面內容，出處：http://download.redis.io/redis-stable/redis.conf

############################## 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

自己翻譯：

默認情況下，Redis 異步保存數據庫到磁盤。這個模式適用於很多應用，但是 Redis 進程出錯或者斷電，會導致幾分鍾的寫數據丟失（依賴於 `save` 配置項）。
AOF 是另一個持久化策略，它提供了更好的持久性。如果使用了默認的 AOF 數據 `fsync` 策略，當斷電或 Redis 服務器進程出錯，Redis 僅丟失一秒鍾的寫數據。
AOF 和 RDB 持久化策略，可以同時啟用。如果啟用了 AOF，Redis 啟動時，將優先使用 AOF 文件進行數據庫還原。