转自http://www.linuxtone.org

一．             LVS+Keepalived 介绍
1.       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）。
 
2.       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. 网站负载均衡拓朴图
 
.
   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
   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
 #   failover@firewall.loc
 #   sysadmin@firewall.loc
   }
   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 LocalAddress:Port Scheduler Flags
 -> RemoteAddress:Port           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。
 
5．停Master服务器的keepalived服务，查看BAKCUP服务器是否能正常接管.
 
 
四．相关参考
 1．LVS 基础知识汇总
Ø         LVS的算法介绍               http://www.linuxtone.org/viewthread.php?tid=69
Ø         学习LVS的三种转发模式       http://www.linuxtone.org/viewthread.php?tid=77
Ø         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
 
3.       Keepalived 相关参考资料。