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基本上都升到php5了

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请教一下楼上的朋友,多台WEB服务器做负载均衡后,如何保证文件的一致性

多台服务器文件一致性的问题核心就是文件分发
这个和同步的时间需求有关
如果在一个不是要求很高的情况下
可以建立一台SVN服务器作为其他所有WEB站点程序的源
然后每次有文件更新之后,check in到SVN里面
再去每台分布的WEB服务器上去做update

如果对于环境要求比较高(任何时候都不能发生数据不同步的问题)
1.可以用SAN.优点是你不用考虑太多东西,把所有的东西都存在对你来说是本地硬盘的SAN上面就可以了.更新也只要更新一份就可以了.
缺点就是成本.以及容灾,如果SAN要做容灾,价格会更高

2.可以用NAS,优点是你可以用比较低廉的价格来达到近乎SAN的效果
缺点,效率比SAN要差很多.好的NAS价格又会比SAN还要贵.而且NAS的协议一般是NFS之类的,不是很可靠.

3.如果做LB,那么可以在更新之前把其他的都下线,先针对一台更新,然后再更新第二台,上线,再更新一台,再上线一台.
缺点,手工操作比较多,第一次更新的时候所有负载都会积压到一台上面,不过这个可以通过调整更新时间来减轻,但是缺点就是要半夜加班.呵呵.


如果是涉及用户上传内容而要保证文件一致性的话
建议是把程序和用户上传内容分开
用户上传会到另一个独立的子域名下
这样以后的架构再扩展也会方便很多
如果只是用SAN或者NAS暂时做存储后端
程序和用户数据还是驼在一起的话
很快你就会碰到扩展问题了,包括存储和性能两方面.

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