一、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）；
十种调度算法（rrr|wrr|lc|wlc|lblc|lblcr|dh|sh|sed|nq）。
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
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． 配置Realserver脚本.
#vi /usr/local/sbin/realserver.sh
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
[code]
#sysctl ?p
#ip addr add 61.164.122.8/32 dev lo
#ip add list 查看是否绑定
2. 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，只需将粗体部分改一下即可.
3. 停掉lvs_dr.sh演示脚本
vi /etc/rc.local
/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.
整个LVS负均衡HA方案，由keepalived.conf一个文件即可搞定！
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://bbs.linuxtone.org/viewthread.php?tid=69
学习LVS的三种转发模式 http://bbs.linuxtone.org/viewthread.php?tid=77
LVS中的IP负载均衡技术 http://bbs.linuxtone.org/viewthread.php?tid=68
Keepalived 相关参考资料。
http://www.keepalived.org/documentation.html
注意:
1.主从LVS是有等级的,主的DOWN后从的顶上;主的修复启动后把控制权从从的抢过来. 所以,不足之处就是用户会话session来回切换,对用户影响较大. 解决方法是:
state 都设置为Backup,在优先级高的那台设置参数nopreempt.
2.centos4.8(centos5.5上编译keepalived会提示type.h错误,需要升级kernel-devel包）
3。在负载均衡器上，为了获得更好的转发性能，硬件防火墙放在负载均衡器的前面,尽量不要使用主机防火墙。防火墙映射80端口，其余web及数据库均藏于防火墙之后'
4.LVS/DR模式下，防火墙后面的WEB服务器需要能通过硬件防火墙连通外网才行。