Memcached 真的过时了吗?

fmms 12年前
     <p>这两年<a href="">Redis</a>火得可以,Redis也常常被当作<a href=""><span class="wp_keywordlink_affiliate">Memcached</span></a>的挑战者被提到桌面上来。关于Redis与Memcached的比较更是比比皆是。然而,Redis真的在功能、性能以及内存使用效率上都超越了Memcached吗?</p>    <p>下面内容来自Redis作者在stackoverflow上的一个回答,对应的问题是《<a href="/misc/goto?guid=4958332656638016485" target="_blank">Is memcached a dinosaur in comparison to Redis?</a>》(相比Redis,Memcached真的过时了吗?)</p>    <ul>     <li><span style="color:#008000;">You should not care too much about performances. Redis is faster per core with small values, but memcached is able to use multiple cores with a single executable and TCP port without help from the client. Also memcached is faster with big values in the order of 100k. Redis recently improved a lot about big values (unstable branch) but still memcached is faster in this use case. The point here is: nor one or the other will likely going to be your bottleneck for the query-per-second they can deliver.</span></li>     <li>没有必要过多的关心性能,因为二者的性能都已经足够高了。由于Redis只使用单核,而Memcached可以使用多核,所以在比较上,平均每一 个核上Redis在存储小数据时比Memcached性能更高。而在100k以上的数据中,Memcached性能要高于Redis,虽然Redis最近 也在存储大数据的性能上进行优化,但是比起Memcached,还是稍有逊色。说了这么多,结论是,无论你使用哪一个,每秒处理请求的次数都不会成为瓶 颈。(比如瓶颈可能会在网卡)</li>     <li><span style="color:#008000;">You should care about memory usage. For simple key-value pairs memcached is more memory efficient. If you use Redis hashes, Redis is more memory efficient. Depends on the use case.</span></li>     <li>如果要说内存使用效率,使用简单的key-value存储的话,Memcached的内存利用率更高,而如果Redis采用hash结构来做key-value存储,由于其组合式的压缩,其内存利用率会高于Memcached。当然,这和你的应用场景和数据特性有关。</li>     <li><span style="color:#008000;">You should care about persistence and replication, two features only available in Redis. Even if your goal is to build a cache it helps that after an upgrade or a reboot your data are still there.</span></li>     <li>如果你对数据持久化和数据同步有所要求,那么推荐你选择Redis,因为这两个特性Memcached都不具备。即使你只是希望在升级或者重启系统后缓存数据不会丢失,选择Redis也是明智的。</li>     <li><span style="color:#008000;">You should care about the kind of operations you need. In Redis there are a lot of complex operations, even just considering the caching use case, you often can do a lot more in a single operation, without requiring data to be processed client side (a lot of I/O is sometimes needed). This operations are often as fast as plain GET and SET. So if you don’t need just GEt/SET but more complex things Redis can help a lot (think at timeline caching).</span></li>     <li>当然,最后还得说到你的具体应用需求。Redis相比Memcached来说,拥有更多的数据结构和并支持更丰富的数据操作,通常在 Memcached里,你需要将数据拿到客户端来进行类似的修改再set回去。这大大增加了网络IO的次数和数据体积。在Redis中,这些复杂的操作通 常和一般的GET/SET一样高效。所以,如果你需要缓存能够支持更复杂的结构和操作,那么Redis会是不错的选择。</li>    </ul>    <p>来源:<a href="/misc/goto?guid=4958332656638016485" target="_blank">Is memcached a dinosaur in comparison to Redis?</a>(其他人的回答同样值得一看)<br /> 本文转载自: <a href="/misc/goto?guid=4958332658172924670" rel="nofollow" target="_blank"></a></p>