背景:
随着你的网站业务量的增长你网站的服务器压力越来越大？需要负载均衡方案！商业的硬件如F5又太贵，你们又是创业型互联公司如何有效节约成本，节省不必要的浪费？同时实现商业硬件一样的高性能高可用的功能？有什么好的负载均衡可伸张可扩展的方案吗？答案是肯定的！有！我们利用 LVS+Keepalived基于完整开源软件的架构可以为你提供一个负载均衡及高可用的服务器。

LVS+Keepalived 介绍
LVS
LVS是Linux Virtual Server的简写，意即Linux虚拟服务器，是一个虚拟的服务器集群系统。本项目在1998年5月由章文嵩博士成立，是中国国内最早出现的自由软件项目之一.目前有三种IP负载均衡技术（VS/NAT、VS/TUN和VS/DR）；
八种调度算法（rr,wrr,lc,wlc,lblc,lblcr,dh,sh）。

Keepalvied
Keepalived在这里主要用作RealServer的健康状态检查以及LoadBalance主机和BackUP主机之间failover的实现
二. 网站负载均衡构架图


IP信息列表：
名称 IP
LVS-DR-Master 61.164.122.6
LVS-DR-BACKUP 61.164.122.7
LVS-DR-VIP 61.164.122.8
WEB1-Realserver 61.164.122.9
WEB2-Realserver 61.164.122.10
GateWay 61.164.122.1
三. 安装LVS和Keepalvied软件包
1. 下载相关软件包

     #mkdir /usr/local/src/lvs
     #cd /usr/local/src/lvs
     #wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.24.tar.gz
     #wget http://www.keepalived.org/software/keepalived-1.1.15.tar.gz

2.安装LVS和Keepalived

        #lsmod |grep ip_vs
        #uname -r
        2.6.18-53.el5PAE
        #ln -s /usr/src/kernels/2.6.18-53.el5PAE-i686/  /usr/src/linux

        #tar zxvf ipvsadm-1.24.tar.gz
        #cd ipvsadm-1.24
        #make && make install
        #find / -name ipvsadm  # 查看ipvsadm的位置

         #tar zxvf keepalived-1.1.15.tar.gz
        #cd keepalived-1.1.15
        #./configure  && make && make install
        #find / -name keepalived  # 查看keepalived位置                
    
         #cp /usr/local/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
        #cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/
        #mkdir /etc/keepalived
        #cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/
        #cp /usr/local/sbin/keepalived /usr/sbin/
        #service keepalived start|stop     #做成系统启动服务方便管理.

四. 配置LVS实现负载均衡
1． LVS-DR，配置LVS脚本实现负载均衡

      #vi /usr/local/sbin/lvs-dr.sh
      #!/bin/bash
        # description: start LVS of DirectorServer
        #Written by :NetSeek http://www.linuxtone.org
        
        GW=61.164.122.1
        # website director vip.
        SNS_VIP=61.164.122.8
        SNS_RIP1=61.164.122.9
        SNS_RIP2=61.164.122.10

        ./etc/rc.d/init.d/functions

        logger $0 called with $1

        case "$1" in

        start)
           # set squid vip
           /sbin/ipvsadm --set 30 5 60
                   /sbin/ifconfig eth0:0 $SNS_VIP broadcast $SNS_VIP netmask 255.255.255.255
        broadcast $SNS_VIP up
           /sbin/route add -host $SNS_VIP dev eth0:0
           /sbin/ipvsadm -A -t $SNS_VIP:80 -s wrr -p 3
           /sbin/ipvsadm -a -t $SNS_VIP:80 -r $SNS_RIP1:80 -g -w 1
           /sbin/ipvsadm -a -t $SNS_VIP:80 -r $SNS_RIP2:80 -g -w 1
           touch /var/lock/subsys/ipvsadm >/dev/null 2>&1

       ;;
        stop)
           /sbin/ipvsadm -C
           /sbin/ipvsadm -Z
           ifconfig eth0:0 down
           ifconfig eth0:1 down
           route del $SNS_VIP
           route del $SS_VIP
           rm -rf /var/lock/subsys/ipvsadm >/dev/null 2>&1
           echo "ipvsadm stoped"
           ;;

        status)

           if [ ! -e /var/lock/subsys/ipvsadm ];then
                echo "ipvsadm stoped"
                exit 1
           else
                echo "ipvsadm OK"
           fi
           ;;

        *)
          echo "Usage: $0 {start|stop|status}"
           exit 1
        esac
        exit 0

2． 配置Realserver脚本.

        #vi /usr/local/sbin/realserver.sh
        #!/bin/bash
        # description: Config realserver lo and apply noarp 
        #Written by :NetSeek http://www.linuxtone.org
        
        SNS_VIP=61.164.122.8
         
        . /etc/rc.d/init.d/functions
         
        case "$1" in
        start)
               ifconfig lo:0 $SNS_VIP netmask 255.255.255.255 broadcast $SNS_VIP
               /sbin/route add -host $SNS_VIP dev lo:0
               echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
               echo "2" >/proc/sys/net/ipv4/conf/lo/arp_announce
               echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore
               echo "2" >/proc/sys/net/ipv4/conf/all/arp_announce
               sysctl -p >/dev/null 2>&1
               echo "RealServer Start OK"
         
               ;;
        stop)
               ifconfig lo:0 down
               route del $SNS_VIP >/dev/null 2>&1
               echo "0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
               echo "0" >/proc/sys/net/ipv4/conf/lo/arp_announce
               echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
               echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
               echo "RealServer Stoped"
               ;;
        *)
               echo "Usage: $0 {start|stop}"
               exit 1
        esac
         
        exit 0

或者采用secondary ip address方式配置

          # vi /etc/sysctl.conf

          net.ipv4.conf.lo.arp_ignore = 1
          net.ipv4.conf.lo.arp_announce = 2
          net.ipv4.conf.all.arp_ignore = 1
          net.ipv4.conf.all.arp_announce = 2

          #sysctl –p
          #ip addr add 61.164.122.8/32 dev lo
          #ip add list 查看是否绑定

3. 启动lvs-dr脚本和realserver启本，在DR上可以查看LVS当前状态:

#watch ipvsadm –ln

五．利用Keepalvied实现负载均衡和和高可用性
1.配置在主负载均衡服务器上配置keepalived.conf

#vi /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   notification_email {
         cnseek@gmail.com
   }
   notification_email_from sns-lvs@gmail.com
   smtp_server 127.0.0.1
  # smtp_connect_timeout 30
   router_id LVS_DEVEL
}

# 20081013 written by :netseek
# VIP1
vrrp_instance VI_1 {
    state MASTER             #备份服务器上将MASTER改为BACKUP   
    interface eth0
    virtual_router_id 51
    priority 100    # 备份服务上将100改为99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        61.164.122.8   
        #(如果有多个VIP，继续换行填写.)
    }
}

virtual_server 61.164.122.8 80 {
    delay_loop 6                  #(每隔10秒查询realserver状态)
    lb_algo wrr                  #(lvs 算法)
    lb_kind DR                  #(Direct Route)
    persistence_timeout 60        #(同一IP的连接60秒内被分配到同一台realserver)
    protocol TCP                #(用TCP协议检查realserver状态)

    real_server 61.164.122.9 80 {
        weight 3               #(权重)
        TCP_CHECK {
        connect_timeout 10       #(10秒无响应超时)
        nb_get_retry 3
        delay_before_retry 3
        connect_port 80
        }
    }
    real_server 61.164.122.10 80 {
        weight 3
        TCP_CHECK {
        connect_timeout 10
        nb_get_retry 3
        delay_before_retry 3
        connect_port 80
        }
     }
}

2. BACKUP服务器同上配置，先安装lvs再按装keepalived,仍后配置/etc/keepalived/keepalived.conf，只需将红色标示的部分改一下即可.
3.

   
   vi /etc/rc.local
   #/usr/local/sbin/lvs-dr.sh  将lvs-dr.sh这个脚本注释掉。步
   #/usr/local/sbin/lvs-dr.sh stop 停止lvs-dr脚本
   #/etc/init.d/keepalived start  启动keepalived 服务，keepalived就能利用

keepalived.conf 配置文件，实现负载均衡和高可用.

4. 查看lvs服务是否正常

#watch ipvsadm –ln

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddressort Scheduler Flags
-> RemoteAddressort Forward Weight ActiveConn InActConn
TCP 61.164.122.8:80 wrr persistent 60
-> 61.164.122.10:80 Route 3 0 0
-> 61.164.122.9:80 Route 3 0 0

#tail –f /var/log/message

监听日志，查看状态，测试LVS负载均衡及高可用性是否有效。

5．停Master服务器的keepalived服务，查看BAKCUP服务器是否能正常接管服务。
四．相关参考
1．LVS 基础知识汇总
LVS的算法介绍 http://www.linuxtone.org/viewthread.php?tid=69
学习LVS的三种转发模式 http://www.linuxtone.org/viewthread.php?tid=77
LVS中的IP负载均衡技术 http://www.linuxtone.org/viewthread.php?tid=68
更多的请到http://www.linuxtone.org 负载均衡版查看

Keepalived 相关参考资料。
http://www.keepalived.org/documentation.html