我们知道,集中式与分布式是当前系统对业务处理最典型的处理方式,两种方式各有其优缺点,这里讨论的是集中式的IDC。所谓IDC大家肯定都不陌生,这类数据中心的架构相对体系比较成熟,具备专业的运维人员,但是由于是集中式,对生产运维人员的压力也就比较大,因为整个IDC对整个企业的业务连续性的影响举足轻重。在这种情况下,IDC的灾备的重要性也就凸显出来。
谈到灾备,不得不谈的两个衡量灾备的可用性的指标RTO,RPO,这两个指标一个是指当灾难发生的时候,灾备系统的恢复需要多长时间,即灾难发生后,经过多长时间,系统可以正常的进行对外业务; 一个是当灾难发生以后,数据需要在生成的时间,这里的在生成的意思是灾难发生后,肯定有数据丢失,灾备系统能保证灾难发生前多少分钟的数据时有效的,这两个指标的具体定义如下:
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Recovery Time Objective (RTO) - This is how long your business can afford to wait for IT
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services to be resumed following a disaster.
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If this number is not clearly stated now, think back to the last time you had a significant
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service outage. How long was that outage, and how much pain did your company suffer as
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a result? This will help you get a feel for whether your RTO should be measured in days,
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hours, or minutes.
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Recovery Point Objective (RPO) - This is how much data your company is willing to
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recreate following a disaster. In other words, what is the acceptable time difference
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between the data in your production system and the data at the recovery site.
当然这两个指标都是越小越好,RTO越小,说明你系统可以更快的对外进行业务,RPO越小说明你的系统数据丢失的越少,因此对业务的影响也就越小。
为了保证了这两个指标的最优实现,这里介绍两种实现方案:GDPS/PPRC,GDPS/XRC
首先介绍GDPS,他就是所谓地理分布式并行系统,主要的功能就是基于某些技术,灾备的自动切换
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Geographically Dispersed Parallel Sysplex (GDPS) is a multi-site application availability
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solution that provides the capability to manage remote copy configuration and storage
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subsystems, automates Parallel Sysplex operational tasks, and performs failure recovery
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from a single point of control, thereby improving application availability and decreasing RTO
GDPS的整体架构图如下:
GDPS对应的术语主要有:
这里我们主要关注的K系统,一级磁盘,二级磁盘,以及master 系统也就是production 系统。
在GDPS下,实现灾备的高可用的RTO,RPO的技术主要有两种,一种是基于硬件实现同步复制的PPRC技术,另一种是基于软硬件技术结合的异步复制 的XRC技术,这两种技术针对的场景略有不同,二者的关系是相辅相成的。
PPRC是有距离限制的,最大距离100KM,XRC技术相对来说距离没有多大的限制。
二者的整体架构如下:
二者的具体的数据流如下:
从上面两幅图,你就对这两种复制技术有一个大体的了解了吧,呵呵
在谈到PPRC的时候,还会涉及到hyperswap技术,这种技术的架构如下:
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GDPS/PPRC HyperSwap
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The GDPS/PPRC HyperSwap function is designed to broaden the continuous availability
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attributes of GDPS/PPRC solutions by extending the Parallel Sysplex redundancy to disk
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subsystems. The HyperSwap function can help significantly increase the speed of switching
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sites and switching disk between sites.
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Figure 7-29 illustrates how applications can access the PPRC copy after a HyperSwap via the
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same set of UCBs. After a data set is allocated by a task, the UCB address cannot be
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changed. With HyperSwap this UCB, instead of mapping the primary device, now maps the
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secondary, without any application task disruption.
上面这段介绍了hyperswap的概念以及作用,即在使用了hyper swap后,你可以在不影响应用的情况,切换primary disk 到PPRC copy,这对应用时完全透明的。
这里这对GDPS 以及涉及的两种技术进行了一个大体的介绍,我想你如果不是专门的存储或是OS人员,这些东西对你理解你系统的灾备,应该有一个简单的入门了吧,呵呵
ref:
ABCs of z/OS System Programming
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