1、RDB：快照

• 時間點問題：比如 8:00開始快照，8:10分才快照成功，那麼快照的是8:00還是8:10分的資料
• 方式：
• save 【命令】　　
• bgsave 【命令】- fork[linux]另起一個子程序，資料隔離（寫時複製）進行資料快照
• save <seconds> <changes> 【配置-注意：這邊實際上呼叫的是bgsave命令】

　　　　　　參考配置檔案中的說明：大概指的是指定時間內至少有多少個數據改變

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

ps:涉及點-父子程序之間，資料隔離&CopyOnWrite（僅寫時複製）

2、AOF：日誌