Redis学习——Redis持久化之RDB备份方式保存数据

--fork的作用是复制一个与当前进程一样的进程。新进程的所有数据（变量、环境变量、程序计数器等）数值都和原进程一致，但是是一个全新的进程，并作为原进程的子进程

--AOF方式，点击这里查看[待补充]！

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

# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
# disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.
stop-writes-on-bgsave-error yes

# Compress string objects using LZF when dump .rdb databases?
# For default that's set to 'yes' as it's almost always a win.
# If you want to save some CPU in the saving child set it to 'no' but
# the dataset will likely be bigger if you have compressible values or keys.
rdbcompression yes

# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.
rdbchecksum yes

# 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 ./

save 900 1
save 300 10
save 60 10000

CONFIG GET dir获取目录
###将备份文件 (dump.rdb) 移动到 redis 安装目录并启动服务即可  或者就在当前目录启动

127.0.0.1:6379> CONFIG GET dir  #获取当前操作的目录
1) "dir"
2) "/root"
127.0.0.1:6379> KEYS *  #redis中存在的key
 1) "myhash"
 2) "k3"
 3) "mylist"
 4) "b1"
 5) "du1"
 6) "k1"
 7) "b4"
 8) "key1"
 9) "d"
10) "myset"
11) "du11"
12) "list"
13) "b3"
14) "du"
15) "b2"
16) "skey"
17) "k2"
127.0.0.1:6379> 

127.0.0.1:6379> SHUTDOWN  #关闭服务器

[root@localhost ~]# pwd  #当前目录是/root
/root
[root@localhost ~]# ll  #下面有dump.rdb这个文件
总用量 52
-rw-------. 1 root root  1208 6月  14 08:10 anaconda-ks.cfg
drwxr-xr-x. 3 root root  4096 6月  17 04:35 dufy
-rw-r--r--. 1 root root   283 6月  19 00:13 dump.rdb
-rw-r--r--. 1 root root 24772 6月  14 08:10 install.log
-rw-r--r--. 1 root root  7690 6月  14 08:09 install.log.syslog

[root@localhost ~]# cd /usr/local/bin/
[root@localhost bin]# pwd
/usr/local/bin
[root@localhost bin]# redis-server /root/dufy/redis/redis-3.0.4/redis.conf
[root@localhost bin]# redis-cli
127.0.0.1:6379> KEYS *   # 这里启动后，查看key没有恢复
(empty list or set)
127.0.0.1:6379> 

127.0.0.1:6379> SHUTDOWN
not connected> exit
[root@localhost bin]# cd /root/
[root@localhost ~]# pwd
/root
[root@localhost ~]# redis-server /root/dufy/redis/redis-3.0.4/redis.conf
[root@localhost ~]# redis-cli
127.0.0.1:6379> KEYS *  #重启后，查看key，发现恢复成功了！
 1) "k1"
 2) "b1"
 3) "key1"
 4) "list"
 5) "du11"
 6) "du1"
 7) "b4"
 8) "k3"
 9) "myhash"
10) "b3"
11) "d"
12) "skey"
13) "mylist"
14) "du"
15) "k2"
16) "b2"
17) "myset"
127.0.0.1:6379> 

 适合大规模的数据恢复

对数据完整性和一致性要求不高

    在一定间隔时间做一次备份，所以如果redis意外down掉的话，就会丢失最后一次快照后的所有修改
    -
    fork的时候，内存中的数据被克隆了一份，大致2倍的膨胀性需要考虑

    save 900 1
    save 300 10
    save 60 10000

  内存中的数据对象 --->rdbsave --> 磁盘中的rdb文件
  内存中的数据对象 <---rdload <-- 磁盘中的rdb文件