注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

和申的个人主页

专注于java开发,1985wanggang

 
 
 

日志

 
 

failover  

2011-10-17 11:05:31|  分类: 名词解释 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

简介

  通俗地说,即当A无法为客户服务时,系统能够自动地切换,使B能够及时地顶上继续为客户提供服务,且客户感觉不到这个为他提供服务的对象已经更换。   这里的A和B可以存在于各种领域,但一般fail-over特指计算机领域的数据库、应用服务、硬件设备等的失效转移。   ------------------------------

详细介绍

  【电脑】失效备援 (为系统备援能力的一种, 当系统中其中一项设备失效而无法运作时, 另一项设备即可自动接手原失效系统所执行的工作)   失效转移(failover)是一种备份操作模式,当主要组件由于失效或预定关机时间的原因而 无法工作时,这种模式中的系统组件(比如处理机、服务器、网络或数据库)的功能被转嫁到二级系统组件。对于希望使系统具有更高的故障容忍力,失效转移是一 定会被经常使用的紧急任务系统的主要部分。这个程序包括自动卸下任务交给备用系统组件,这样程序对于终端用户能够尽可能的无故障。失效转移能应用于系统的 许多方面:举个例子,在个人电脑内部,失效转移也许是保护故障的处理机的一种机制;在网络内部,失效转移能够应用于许多网络组件或系统组件,比如连接通 路、存储设备或者环球网服务器。   最初,存储数据在非常基本的配置下被连接到服务器:点对点或者交叉连接。在这种环境下,单一服 务器的故障常常使得大量的用户无法访问数据,直到那个服务器重新在线服务。近来有更多的发展,比如存储区域网络(SAN),在服务器和数据存储系统之中建 立许多到许多的连通性。通常,存储网络在服务器和系统之间使用许多通路(每个通路由包括所有有关组件的完全的配置组成)。一个失效的通路可能是由于通路上 一些单独组件的故障。多重连接通路(每个通路都有多余组件)常常帮助确保线路在一个(或多个)通路失效情况下仍然可行。自动失效转移的能力在于尽管由于设 备问题导致必然的故障然而正常功能仍能被维持。   CISCO PIX/ASA Failover 技术   CISCO PIX/ASA Failover 技术:   是一项故障转移配置的技术,需要两台完全一样的设备,通过一个连接,连接到对方(这个连接也叫 心跳线)。该技术用到的两台设备分为 主用和备用,备用处于待机状态。当主用设备故障后,备用设备可启用,并设置为主用,运行自主用设备复制过来的配置(配置是跟随主用设备移动的)。   CISCO的配置命令:   asa1(config­if)# failover lan enable //启用基于LAN的Failover   asa1(config)# failover lan unit primary //指定设备的角色   asa1(config)# failover lan interface failover e3 //指定Failover 接口   INFO: Non­failover interface config is cleared on Ethernet3 and its sub­interfaces   asa1(config)# failover interface ip failover 192.168.1.1 255.255.255.0 stan 192.168.1.2 //配置Failover IP地址;   asa1(config)# failover lan key ccxx //配置Failover key   asa1(config)# failover //启用Failover;注意,此命令一定要先在Active上输入,否则会引起配置拷错;   将一个接口指定为failover 接口后,再show inter 的时候,该接口就显示为:   interface Ethernet3   description LAN Failover Interface   配置ASA2(standby)   pixfirewall(config)# inte e3   pixfirewall(config­if)# no shut   pixfirewall(config­if)# exit   pixfirewall(config)# failover lan enable   pixfirewall(config)# failover lan unit secondary   pixfirewall(config)# failover lan interface failover e3   INFO: Non­failover interface config is cleared on Ethernet3 and its sub­inter   pixfirewall(config)# failover inter ip failover 192.168.1.1 255.255.255.0 stand 192.168.1.2   pixfirewall(config)# failover key ccxx   pixfirewall(config)# failover   pixfirewall(config)# .   CISCO PIX/ASA Failover 技术也可以在多个CONTEXT上运行,从而实现负载和冗余功能。

相关技术

  心跳线   连接工作机与备份机的网线,通过软件的方式监视工作机,备份机一旦发现工作机由于某种原因停止服务,则立即投入使用,以保证网络的畅通和服务的正常运行.   心跳线是用于连接A、B两台服务器间的网线。在这两台服务器A、B中,A为工作机,B为备份 机,它们之间通过一根心跳线来连接。一般在服务器上都配有两块网卡,其中一块专门用于两台服务器(节点)间的通讯。安装在服务器上的软件通过心跳线来实时 监测对方的运行状态。一旦正在工作的主机A因为各种硬件故障,如电源失效、主要部件失效或者启动盘失效等导致系统发生故障,心跳线会反映给互为备份的另外 一台主机,主机B可以立即投入工作。这样可以在最大限度上保证网络的正常运行。这也称为“心跳检测”。心跳线主要利用一条RS-233检测链路来完成,采 用Ping方式检测验证系统Down机检测的准确性。


Failover

From Wikipedia, the free encyclopedia

In computing, failover is the capability to switch to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the previously active application,[1] server, system, or network. Failover happens without human intervention and generally without warning, unlike switchover.

Systems designers usually provide failover capability in servers, systems or networks requiring continuous availability and a high degree of reliability.

At server-level, failover automation takes place using a "heartbeat" cable that connects two servers. As long as a regular "pulse" or "heartbeat" continues between the main server and the second server, the second server will not initiate its systems. There may also be a third "spare parts" server that has running spare components for "hot" switching to prevent down time.

The second server will immediately take over the work of the first as soon as it detects an alteration in the "heartbeat" of the first machine. Some systems have the ability to page or send a message to a pre-assigned technician or center.

Some systems, intentionally, do not failover entirely automatically, but require human intervention. This "automated with manual approval" configuration runs automatically once a human has approved the failover.

Failback, conversely, involves the process of restoring a system/component/service in a state of failover back to its original state (before failure).

The use of virtualization software has allowed failover practices to become less reliant on physical hardware.

Contents


Failover types

Failover in Disaster Recovery

There are two types of failover:

  1. Automatic Failover: Automatic ERSON-Failover where two servers are located in two different geographic locations. If disaster happens at host site, the secondary server will take over automatically without user or support intervention. In this case, usually, they have online data replication from host to the surviving recovery site, or using clustering technology to failover to secondary server. Of course, there are also other high-availability technologies such as hyperV or VMware, which cause a very minimum interruption and business can resume as normal. This solution is primarily used for high-reliability/critical applications or systems.
  2. Manual Failover: In this case, user or support team intervention is necessary. For example, if an abnormality occurs at a host site, the support team has to restore the database manually at the surviving site, then switch users to the recovery site to resume business as usual. This is also known as a backup and restore solution, which is usually used for non-critical applications or systems.
Fallback in Disaster Recovery

There are also two types of fallback:

  1. After a term that is used for any disaster recovery test that failed, the fallback or revert back will take place
  2. After recovery is completed, Fallback or back to normalcy take place. Failback is the term that is actually used for fallback, but failback means that there are two recovery sites. In another words, this is the 2nd disaster recovery site.

In short,

  1. Failover (Automatic or manual) - from host to recovery site
  2. Fallback (Automatic or manual) – from recovery site to host
  3. Failback (Automatic or manual) – from recovery site 1 to recovery site 2

References

  1. ^ For application-level failover, see for example Jayaswal, Kailash (2005). "27". Administering Data Centers: Servers, Storage, And Voice Over IP. Wiley-India. p. 364. ISBN 9788126506880. Retrieved 2009-08-07. "Although it is impossible to prevent some data loss during an application failover, certain steps can [...] minimize it.".

See also

  评论这张
 
阅读(1296)| 评论(0)
推荐 转载

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2016