转载自：http://blog.sina.com.cn/s/blog_636415010101970j.html
# When running daemonized, Redis writes a pid file in /var/run/redis.pid by # default. You can specify a custom pid file location here. #当 Redis 以守护进程的方式运行的时候，Redis 默认会把 pid 文件放在/var/run/redis.pid #可配置到其他地址，当运行多个 redis 服务时，需要指定不同的 pid 文件和端口 pidfile /var/run/redis.pid
# Accept connections on the specified port, default is 6379. # If port 0 is specified Redis will not listen on a TCP socket. #端口 port 6379
# If you want you can bind a single interface, if the bind option is not # specified all the interfaces will listen for incoming connections. #指定Redis可接收请求的IP地址,不设置将处理所有请求,建议生产环境中设置 # bind 127.0.0.1
# Close the connection after a client is idle for N seconds (0 to disable) #客户端连接的超时时间,单位为秒,超时后会关闭连接 timeout 0
# Set server verbosity to 'debug'# it can be one of:# debug (a lot of information, useful for development/testing)# verbose (many rarely useful info, but not a mess like the debug level)# notice (moderately verbose, what you want in production probably)# warning (only very important / critical messages are logged)#日志记录等级，4个可选值loglevel notice
# Specify the log file name. Also 'stdout' can be used to force # Redis to log on the standard output. Note that if you use standard # output for logging but daemonize, logs will be sent to /dev/null #配置 log 文件地址,默认打印在命令行终端的窗口上，也可设为/dev/null屏蔽日志、 logfile stdout
# Set the number of databases. The default database is DB 0, you can select # a different one on a per-connection basis using SELECT where # dbid is a number between 0 and 'databases'-1 #设置数据库的个数,可以使用 SELECT 命令来切换数据库。 databases 16
# # Save the DB on disk: # #
# 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. #在进行镜像备份时,是否进行压缩 rdbcompression yes
# The filename where to dump the DB #镜像备份文件的文件名 dbfilename dump.rdb
# The working directory. # # The DB will be written inside this directory, with the filename specified # above using the 'dbfilename' configuration directive. #
# Master-Slave replication. Use slaveof to make a Redis instance a copy of # another Redis server. Note that the configuration is local to the slave # so for example it is possible to configure the slave to save the DB with a # different interval, or to listen to another port, and so on. #设置该数据库为其他数据库的从数据库 #slaveof <masterip> <masterport> 当本机为从服务时，设置主服务的IP及端口 # slaveof
# If the master is password protected (using the "requirepass" configuration # directive below) it is possible to tell the slave to authenticate before # starting the replication synchronization process, otherwise the master will # refuse the slave request. #指定与主数据库连接时需要的密码验证 #masterauth <master-password> 当本机为从服务时，设置主服务的连接密码 # masterauth
# When a slave lost the connection with the master, or when the replication# is still in progress, the slave can act in two different ways:## 1) if slave-serve-stale-data is set to 'yes' (the default) the slave will#
# Require clients to issue AUTH before processing any other # commands.
# Set the max number of connected clients at the same time. By default there # is no limit, and it's up to the number of file descriptors the Redis process # is able to open. The special value '0' means no limits. # Once the limit is reached Redis will close all the new connections sending # an error 'max number of clients reached'. #限制同时连接的客户数量。 #当连接数超过这个值时，redis 将不再接收其他连接请求，客户端尝试连接时将收到 error 信息 # maxclients 128
# Don't use more memory than the specified amount of bytes. # When the memory limit is reached Redis will try to remove keys # accordingly to the eviction policy selected (see maxmemmory-policy). # # If Redis can't remove keys according to the policy, or if the policy is # set to 'noeviction', Redis will start to reply with errors to commands # that would use more memory, like SET, LPUSH, and so on, and will continue # to reply to read-only commands like GET. # # This option is usually useful when using Redis as an LRU cache, or to set # an hard memory limit for an instance (using the 'noeviction' policy). # # WARNING: If you have slaves attached to an instance with maxmemory on, # the size of the output buffers needed to feed the slaves are subtracted # from the used memory count, so that network problems / resyncs will # not trigger a loop where keys are evicted, and in turn the output # buffer of slaves is full with DELs of keys evicted triggering the deletion # of more keys, and so forth until the database is completely emptied. # # In short... if you have slaves attached it is suggested that you set a lower # limit for maxmemory so that there is some free RAM on the system for slave # output buffers (but this is not needed if the policy is 'noeviction'). #设置redis能够使用的最大内存。 #达到最大内存设置后，Redis会先尝试清除已到期或即将到期的Key（设置过expire信息的key） #在删除时,按照过期时间进行删除，最早将要被过期的key将最先被删除 #如果已到期或即将到期的key删光，仍进行set操作，那么将返回错误 #此时redis将不再接收写请求,只接收get请求。 #maxmemory的设置比较适合于把redis当作于类似memcached 的缓存来使用 # maxmemory
# By default Redis asynchronously dumps the dataset on disk. If you can live # with the idea that the latest records will be lost if something like a crash # happens this is the preferred way to run Redis. If instead you care a lot # about your data and don't want to that a single record can get lost you should # enable the append only mode: when this mode is enabled Redis will append # every write operation received in the file appendonly.aof. This file will # be read on startup in order to rebuild the full dataset in memory. # # Note that you can have both the async dumps and the append only file if you # like (you have to comment the "save" statements above to disable the dumps). # Still if append only mode is enabled Redis will load the data from the # log file at startup ignoring the dump.rdb file. # # IMPORTANT: Check the BGREWRITEAOF to check how to rewrite the append # log file in background when it gets too big. #redis
# The name of the append only file (default: "appendonly.aof")##更新日志文件名，默认值为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
# Virtual Memory allows Redis to work with datasets bigger than the actual # amount of RAM needed to hold the whole dataset in memory. # In order to do so very used keys are taken in memory while the other keys # are swapped into a swap file, similarly to what operating systems do # with memory pages. # # To enable VM just set 'vm-enabled' to yes, and set the following three # VM parameters accordingly to your needs. #是否开启虚拟内存支持。 #redis 是一个内存数据库，当内存满时,无法接收新的写请求,所以在redis2.0后,提供了虚拟内存的支持 #但需要注意的，redis 所有的key都会放在内存中，在内存不够时,只把value 值放入交换区 #虽使用虚拟内存，但性能基本不受影响，需要注意的是要把vm-max-memory设置到足够来放下所有的key vm-enabled no # vm-enabled yes
# This is the path of the Redis swap file. As you can guess, swap files # can't be shared by different Redis instances, so make sure to use a swap # file for every redis process you are running. Redis will complain if the # swap file is already in use. # # The best kind of storage for the Redis swap file (that's accessed at random)
# vm-max-memory configures the VM to use at max the specified amount of # RAM. Everything that deos not fit will be swapped on disk *if* possible, that # is, if there is still enough contiguous space in the swap file. # # With vm-max-memory 0 the system will swap everything it can. Not a good # default, just specify the max amount of RAM you can in bytes, but it's # better to leave some margin. For instance specify an amount of RAM # that's more or less between 60 and 80% of your free RAM. #设置开启虚拟内存后,redis将使用的最大物理内存大小。 #默认为0，redis将把他所有能放到交换文件的都放到交换文件中，以尽量少的使用物理内存 #即当vm-max-memory设置为0的时候,其实是所有value都存在于磁盘 #在生产环境下,需要根据实际情况设置该值,最好不要使用默认的 0 vm-max-memory 0
# Redis swap files is split into pages. An object can be saved using multiple # contiguous pages, but pages can't be shared between different objects. # So if your page is too big, small objects swapped out on disk will waste # a lot of space. If you page is too small, there is less space in the swap # file (assuming you configured the same number of total swap file pages). # # If you use a lot of small objects, use a page size of 64 or 32 bytes. # If you use a lot of big objects, use a bigger page size. # If unsure, use the default :) #设置虚拟内存的页大小 如果 value 值比较大,如要在 value 中放置博客、新闻之类的所有文章内容，就设大一点 vm-page-size 32
# Number of total memory pages in the swap file. # Given that the page table (a bitmap of free/used pages) is taken in memory, # every 8 pages on disk will consume 1 byte of RAM. # # The total swap size is vm-page-size * vm-pages # # With the default of 32-bytes memory pages and 134217728 pages Redis will # use a 4 GB swap file, that will use 16 MB of RAM for the page table. # # It's better to use the smallest acceptable value for your application, # but the default is large in order to work in most conditions. #设置交换文件的总的 page 数量 #注意page table信息是放在物理内存中，每8个page 就会占据RAM中的 1 个 byte #总的虚拟内存大小 = vm-page-size * vm-pages vm-pages 134217728
# Max number of VM I/O threads running at the same time. # This threads are used to read/write data from/to swap file, since they # also encode and decode objects from disk to memory or the reverse, a bigger # number of threads can help with big objects even if they can't help with # I/O itself as the physical device may not be able to couple with many # reads/writes operations at the same time. # # The special value of 0 turn off threaded I/O and enables the blocking # Virtual Memory implementation. #设置 VM IO 同时使用的线程数量。 vm-max-threads 4
# Hashes are encoded in a special way (much more memory efficient) when they # have at max a given numer of elements, and the biggest element does not # exceed a given threshold. You can configure this limits with the following # configuration directives. #redis 2.0后引入了 hash 数据结构。
# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in # order to help rehashing the main Redis hash table (the one mapping top-level # keys to values). The hash table implementation redis uses (see dict.c) # performs a lazy rehashing: the more operation you run into an hash table # that is rhashing, the more rehashing "steps" are performed, so if the # server is idle the rehashing is never complete and some more memory is used # by the hash table. #
Redis官方文档对VM的使用提出了一些建议:
- 当key很小而value很大时,使用VM的效果会比较好.因为这样节约的内存比较大
- 当key不小时,可以考虑使用一些非常方法将很大的key变成很大的value,如可将key,value组合成一个新的value
- 最好使用linux ext3 等对稀疏文件支持比较好的文件系统保存你的swap文件
- vm-max-threads参数可设置访问swap文件的线程数，最好不要超过机器的核数；设置为0则所有对swap文件的操作都是串行的，可能会造成比较长时间的延迟,但是对数据完整性有很好的保证
- save seconds updates，save配置，指出在多长时间内，有多少次更新操作，就将数据同步到数据文件。可多个条件配合，默认配置了三个条件。
- appendonly yes/no ，appendonly配置，指出是否在每次更新操作后进行日志记录，如果不开启，可能会在断电时导致一段时间内的数据丢失。因为redis本身同步数据文件是按上面的save条件来同步的，所以有的数据会在一段时间内只存在于内存中。
- appendfsync no/always/everysec ，appendfsync配置，no表示等操作系统进行数据缓存同步到磁盘，always表示每次更新操作后手动调用fsync()将数据写到磁盘，everysec表示每秒同步一次。