LVS基于NAT模式搭建负载均衡群集

LVS的基本架构图

负载均衡群集中，包括三个层次的组件：

1、第一层，负载调度器（BL）

前段至少有一个负载调度器（Load Balancer 或称为Director）负责响应并分发来自客户端的访问请求。

这是访问整个集群系统的唯一入口，对外使用所有服务器共有的VIP（Virtual IP，虚拟IP）地址，也称为群集IP地址，通常会配置主、备两台调度器实现热备份，当主机调度器失效以后平滑替换至备用调度器，确保高可用性。

2、第二层，服务器池(Real Server)

后端由大量真实服务器（Real Server）构成服务器池（Server Pool），提供实际的应用服务，整个群集的伸缩性通过增加、删除服务器节点来完成，而这些过程对客户机是透明的。

群集所提供的应用服务（如HTTP、FTP）由服务器池承担，其中的每个节点具有独立的RIP（Real IP，真实IP）地址，只处理调度器分发过来的客户机请求。当某个节点暂时失效时，负载调度器的容错机制会将其隔离，等待错误排除以后再重新纳入服务器池。

3、第三层，共享储存（NFS）

为了保持服务的一致性，所有节点使用共享储存设备。

为了服务器池中的所有节点提供稳定、一致的文件存取服务，确保整个集群的统一性。在Linux/UNIX环境中，共享储存可以使用NAS设备，或者提供NFS（Network File System，网络文件系统）共享服务的专用服务器。

实验环境：

LVS调度器（BL）作为Web1、Web2两台Web服务器池的网关

BL两块网卡，分别连接内外网   （本次实验是单节点调度的，若要高可用请添加多台备用调度器+keepalive实现，本次实验只是做负载均衡）

BL主机（负载调度器）：

外网地址：192.168.10.20/24，同时也作为整个群集的VIP

内网地址：192.168.1.11/24

Web1主机：192.168.1.22/24

Web2主机：192.168.1.33/24

NFS主机：192.168.1.44/24

使用轮询（rr）调度算法

主机名称	内网IP地址	外网IP地址	部署软件
LVS-master（BL主机）	192.168.1.11	192.168.10.20	ipvsadm
NFS	192.168.1.22	无	nfs、rpcbind
WEB1	192.168.1.33	无	httpd、nfs-utils
WEB2	192.168.1.44	无	httpd、nfs-utils

LVS的NAT负载均衡模式原理：

1、PC机直接访问BL服务器的VIP：192.168.10.20

2、BL服务器接收到请求后，通过自身调度算法选择一台下面的WEB服务器，并将目标地址为某一WEB服务器的IP，源地址不变。

3、WEB服务器接受到请求后，将数据包解封并返回数据给BL，返回的数据包中，源IP为WEB自身IP，目标IP为PC机IP。

4、BL服务器接收到WEB响应的数据包后，将数据包的源IP改为自身IP，目标IP不变，发给PC机

整个过程PC机并不知道WEB服务器的存在。

 

开始搭建

1、配置NAS（nfs）共享储存服务器

 [root@nfs ~]# yum -y install nfs-utils rpcbind    #下载NFS rpcbind
 [root@nfs ~]# mkdir /opt/www
 [root@nfs ~]# vim /etc/exports                    #设置共享目录，将/opt/www作为共享目录，要求192.168.2.0/24网段只读权限访问网页数据（若增加读写速度和安全性，可结合raid5+LVM）
 /opt/www        192.168.1.0/(ro,sync,no_root_squash)
 [root@nfs ~]# /etc/init.d/rpcbind start
 正在启动 rpcbind：                                         [确定]
 [root@nfs ~]# /etc/init.d/nfs start
 启动 NFS 服务：                                            [确定]
 启动 NFS mountd：                                          [确定]
 启动 NFS 守护进程：                                        [确定]
 正在启动 RPC idmapd：                                      [确定]
 [root@nfs ~]# showmount -e 192.168.1.22            #查看nfs挂载情况
 Export list for 192.168.1.22:
 /opt/www 192.168.1.0/
 [root@nfs ~]# chkconfig rpcbind on   #设置开机启动
 [root@nfs ~]# chkconfig nfs on       #设置开机启动
 [root@nfs ~]# echo "<h1>it works</h1>">/opt/www/index.html   #编辑共享文件内容

2、配置WEB1、WEB2（操作相同）

 [root@WEB1 ~]#yum -y install httpd nfs-utils                   #下载Apache、nfs服务
 [root@WEB1 ~]#sed -i '/#S/ s/#//' /etc/httpd/conf/httpd.conf   #启用apache的域名服务
 [root@WEB1 ~]#sed -n '/com:80/p' /etc/httpd/conf/httpd.conf
 ServerName www.example.com:
 [root@WEB1 ~]# /etc/init.d/httpd start
 正在启动 httpd：                                           [确定]
 
 [root@WEB1 ~]# vim /etc/fstab           #编辑fstab文件，写入nfs服务器的挂载目录，使其永久生效。
 ……
 192.168.1.22:/opt/www/   /var/www/html/          nfs     defaults,_netdev
 #挂载点IP：挂载点目录       #挂载到的目录            
 
 [root@WEB1 ~]# mount -a    #挂载所以可挂载点
 [root@WEB1 ~]# df -hT      #查看挂载情况
 Filesystem                 Type   Size  Used Avail Use% Mounted on
 /dev/mapper/vg_www-lv_root ext4    37G  .3G   34G   % /
 /dev/sda1                  ext4   485M   33M  427M   % /boot
 tmpfs                      tmpfs  242M       242M   % /dev/shm
 192.168.1.22:/opt/www/      nfs     37G  1.3G   34G   4% /var/www/html

3、PC机访问WEB服务器测试

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" alt="" />

 4、配置LVS服务器（BL）

 （）加载ip_vs模块，安装ipvsadm工具
 [root@bl ~]# modprobe ip_vs
 [root@bl ~]# cat /proc/net/ip_vs
 IP Virtual Server version 1.2. (size=)
 Prot LocalAddress:Port Scheduler Flags
   -> RemoteAddress:Port Forward Weight ActiveConn InActConn
 [root@bl ~]# yum -y install ipvsadm
 
 （）配置负载调度器SNAT转发规则
 [root@bl ~]# /etc/init.d/ipvsadm stop
 ipvsadm: Clearing the current IPVS table:                  [确定]
 ipvsadm: Unloading modules:                                [确定]
 [root@bl ~]# ipvsadm -A -t 192.168.10.20: -s rr
 [root@bl ~]# ipvsadm -a -t 192.168.10.20: -r 192.168.1.33: -m -w
 [root@bl ~]# ipvsadm -a -t 192.168.10.20: -r 192.168.1.44: -m -w
 [root@bl ~]# ipvsadm -L -n
 IP Virtual Server version 1.2. (size=)
 Prot LocalAddress:Port Scheduler Flags
   -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
 TCP  192.168.10.20: rr
   -> 192.168.1.33:               Masq
   -> 192.168.1.44:               Masq
 [root@bl ~]#ipvsadm -S >> /etc/sysconfig/ipvsadm
 ipvsadm: Saving IPVS table to /etc/sysconfig/ipvsadm:      [确定]
 [root@bl ~]# chkconfig ipvsadm on
 
 （）开启路由转发功能
 [root@bl ~]#echo "net.ipv4.ip_forward=1
 net.ipv4.conf.all.rp_filter=
 net.ipv4.conf.default.rp_filter= " > /etc/sysctl.conf  
 
 [root@bl ~]# sysctl -p
 net.ipv4.ip_forward =
 net.ipv4.conf.all.rp_filter =
 net.ipv4.conf.default.rp_filter = 

5、PC机访问VIP测试

（若不成功，检查各个服务器的防火墙与selinux机制是否关闭）多刷新几次

多次CTRL+f5刷新后查看

  [root@bl ~]#ipvsadm -L -n -c
  IPVS connection entries
  pro expire state       source               virtual            destination
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.33:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.33:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.44:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.44:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.44:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.33:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.33:
  TCP :  TIME_WAIT   192.168.10.10: 192.168.10.20:    192.168.1.33:

之所以看到的结果并不是轮询的一次是192.168.1.33下一次是192.168.1.44，是因为负载调度器要判断一次完整TCP连接结束后才会进行轮询，也就是完成完整的三次握手与四次断开，因此若在网页上下载电影时及时刷新了网页，也不会轮询到下一台服务器导致传输中断。

Have fun!!!