redis 配置文件 append only file(aof)部分---数据持久化
2013-04-09 10:09
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上一篇翻译之后,发觉通过翻译虽然比较吃力(不熟悉,多练习应该可以更熟练),但是能够较好的帮助理解redis的功能,遂继续翻译了aof部分,如下
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############################## 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 # 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 to wait 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 always # appendfsync no # When the AOF fsync policy is set to always or everysec, and a background # saving process (a background save or AOF log background rewriting) is # performing a lot of I/O against the disk, in some Linux configurations # Redis may block too long on the fsync() call. Note that there is no fix for # this currently, as even performing fsync in a different thread will block # our synchronous write(2) call. # # In order to mitigate this problem it's possible to use the following option # that will prevent fsync() from being called in the main process while a # BGS***E or BGREWRITEAOF is in progress. # # This means that while another child is saving, the durability of Redis is # the same as "appendfsync none". In practical terms, this means that it is # possible to lose up to 30 seconds of log in the worst scenario (with the # default Linux settings). # # If you have latency problems turn this to "yes". Otherwise leave it as # "no" that is the safest pick from the point of view of durability. no-appendfsync-on-rewrite no # Automatic rewrite of the append only file. # Redis is able to automatically rewrite the log file implicitly calling # BGREWRITEAOF when the AOF log size grows by the specified percentage. # # This is how it works: Redis remembers the size of the AOF file after the # latest rewrite (if no rewrite has happened since the restart, the size of # the AOF at startup is used). # # This base size is compared to the current size. If the current size is # bigger than the specified percentage, the rewrite is triggered. Also # you need to specify a minimal size for the AOF file to be rewritten, this # is useful to avoid rewriting the AOF file even if the percentage increase # is reached but it is still pretty small. # # Specify a percentage of zero in order to disable the automatic AOF # rewrite feature. auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb
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############################## 仅追加方式 ############################### #默认情况下Redis会异步的将数据导出到磁盘上。这种模式对许多应用程序已经足够了, #但是如果断电或者redis进程出问题就会导致一段时间内的更新数据丢失(取决与配置项) # #这种只增文件是可选的能够提供更好的体验的数据持久化策略。 #举个例子,如果使用默认的配置数据fsync策略,在服务器意外断电的情况下redis只会丢失一秒中内的更新数据, #或者当redis进程出问题但操作系统运转正常时,redis只会丢失一个数据更新操作。 # #AOF 和 RDB 持久化方式可以同时启动并且无冲突。 #如果AOF开启,启动redis时会加载aof文件,这些文件能够提供更好的保证。 #请在 http://redis.io/topics/persistence 获取更多数据持久化信息。 appendonly no # 只增文件的文件名称。(默认是appendonly.aof) # appendfilename appendonly.aof #调用fsync()函数会通知操作系统真正将数据写入磁盘,而不是等待缓冲区中有更多数据。 #有些操作系统会将数据输出到磁盘,有些操作系统只是ASAP。 # #redis支持三种不同的方式: # #no:不调用,之等待操作系统来清空缓冲区当操作系统要输出数据时。很快。 # always: 每次更新数据都写入仅增日志文件。慢,但是最安全。 # everysec: 每秒调用一次。折中。 # #默认是每秒中一次,因为它往往是在速度和数据安全两者之间的折中选择。 #如果你可以接受让操作系统去自动清空缓存,你可以将这项配置降低到'no'(如果你可以接受一段时间的数据丢失,默认的rdb就足够了), #这完全取决与你。如果你想要一个更好的体验或者从相反的角度,使用'always',这样会很慢,但是比'everysec'安全些。 # #请在下面的文章中获取更多细节知识: # http://antirez.com/post/redis-persistence-demystified.html # #如果你不是很清楚这三项之间的区别,或者不知道哪种适合你的机器,就是用默认吧。 # appendfsync always appendfsync always # appendfsync no #当AOF策略设置为'always'或者'everysec'的时候,后台的保存进程会进行很多磁盘I/O操作, #在某些linux结构中redis会在调用sync()方法时阻塞很长时间。记住,现在还没办法解决这个问题,即使在不同进程中进行调用也会block。 # #使用如下配置可能会缓解这个问题,这样会在存储大数据或者BIGREWRITEAOF的时候不会在主进程中调用fsync()方法。 # # 这表示,如果另外一个子进程在进行保存操作,redis的表现如同配置为‘appendfsync no’。 #在实际应用中,这表示在最坏的情景下(使用linux默认配置)可能会丢失30秒日志。 # #如果你有特殊的情况可以配置为'yes'。但是配置为'no'是最为安全的选择。 no-appendfsync-on-rewrite no #自动重写只增文件。 #redis可以自动盲从的调用‘BGREWRITEAOF’来重写日志文件,如果日志文件增长了指定的百分比。 # #它是这样工作的:每次rewrite后redis会记录日志文件的大小。(如果重启后没有重写后的大小,就默认用日志文件大小) # # 这个基准日志大小和当前日志大小做比较。如果当前大小比指定的百分比,重写机制就会被触发。 #同时,你也要制定一个重写下线,用来避免增长百分比够了,但是日志文件还很小的情况。 # #指定百分比为0可以注掉自动重写日志文件功能。 auto-aof-rewrite-percentage 100 auto-aof-rewrite-min-size 64mb
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