Admin Alert: Redundancy is Good, Redundancy is Good, Re…
June 18, 2008 Joe Hertvik
The next time you order a Power i upgrade, pay special attention to the redundant components that are available. As the computing world moves toward more and more redundancy options, many 24×7 i5/OS shops are requiring absolute redundancy in almost everything available. This week, I’ll look at some of the redundancy options available for i5/OS machines and how they can help your shop.
The math of redundancy is simple. If it costs 10 percent more to install redundant components, for example, how much will that save the company if it keeps a critical system running during a busy period? Will it cost less than if the servers go down for an extended period of time without a high availability solution in place for rapid recovery? For many shops, the math does add up and there’s no question of cost or whether or not they should put in redundant components. They just do it.
But if you’re wondering how you can protect your Power i platform from various failures as you upgrade your machine, here are some suggestions for how to put the power of redundancy to work in your organization.
The Hierarchy of Redundant Electricity
With any enterprise computing system, the easiest crash to prevent is the one caused by power failure (although the solutions can be costly). There are a number of techniques for rescuing your Power i from sudden power outages that can take down your business in a literal flash. By increasing order of protection, here’s a hierarchical ladder of power protection strategies that you can implement to keep your i5/OS and OS/400 machines running.
Disk Drive Redundancy
Like many other systems, Power i, System i, and iSeries machines offer RAID 5 and mirroring protection in order to protect your machine against a disk drive crash. RAID 5 recreates the data from a failed disk drive, while mirroring creates an exact copy of your disk set that can be used in an emergency. For i5/OS V5R3 and above, IBM now offers new DASD IOAs and features that support RAID 6 protection. Like RAID 5, RAID 6 protects data from being lost through disk failure. However, RAID 6 protection extends to two disk drives failing in a RAID set rather than the one-disk protection that RAID 5 offers.
Data Redundancy in a Cluster
In multiple system environments, IBM offers the option of creating a collection or binding a group of multiple systems together to form a cluster. Clustered systems work together as a single system to provide almost 100 percent availability for critical applications and data, simplify systems management, and increase system scalability. A cluster can contain up to 128 systems. To learn more about clusters, check out the IBM Information Center topic Availability for multiple systems: Clusters.
To enhance high availability in a clustered environment, IBM offers several different data resilience technologies that protect data and allow data access at all times. According to IBM, data resilience refers to “the ability for the data to remain accessible to the application even if the system that originally hosted the data failed.” These technologies include data replication, switchable disk pools, cross-site mirroring, and the Copy Services function provided with IBM System Storage DS products. To learn more about IBM’s data resilience options, check out the IBM Information Center topic Data resilience solutions for i5/OS clusters.
If a clustering environment is too expensive to implement and it’s critical that your system always remain up, you can investigate purchasing and installing a Capacity BackUp (CBU) system Power i box. (See my article Five Benefits of a High Availability System for more on CBU.) A CBU is basically a system in waiting on your network. With the use of high availability software from companies such as Vision Solutions, IBM’s DataMirror, and Bug Busters Software Engineering, the CBU contains an almost up-to-date copy of your applications and your data. When disaster hits and the production box isn’t available (such as during a hurricane, flood, or fire), you can fail over to the CBU, the CBU impersonates your downed production box, and you restart processing.
The CBU can be located on-site, or it may be hosted at a remote location. Some companies host their CBUs at sister locations, since those locations are already hooked up to the internal network. Other companies may hire a company that provides hosting services to co-locate their CBU.
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