Published : 2016-12-09.
Last updated : 2017-05-02.
Business Continuity Management Example: selection process failure preparation.
When you look at picture 1, the same decision arguments (Business Impact and Critical Time span) can be seen as in Picture 1 in the article "Business Continuity Management Example: selection process disaster / calamity preparation."
These arguments are now applied to the situation that one of the server systems fails at the primary location. Of course you can have other or more decision arguments in your organization.
Picture 1. Example: selection process failure preparation.
When you own virtualization technology such as VMware or Hyper-V, this opens additional opportunities for high availability of the server systems. By deploying multiple identical redundant hardware servers, a virtual server can be moved (using VMotion or "Live Migration") to another server with sufficient capacity at an impending failure of a server or hardware maintenance. Since virtualization makes it easy to quickly add virtual server systems, one must ensure that there is enough spare capacity to handle failures.
No spare server system can be a valid choice when thorough analysis shows that the daily business minimally depends on this server system. Only in the event of a failure replacement parts or systems are purchased. The main advantage of this strategy is the low preparation cost.
In the case of a hosting situation, for example, you can fall back on spare (virtual) machines that your hoster has "on the shelf" to solve his own system failures. You can also contact an organization to maintain a spare server system and share the costs. Calamity service providers rely on this principle in order to manage costly systems efficiently considering the fact that their customers have a wide regional spread. Both parties of the shared arrangements may not use these spare resources for normal production environments.
Should you have a secondary-or backup site, you can decide to move an installed server system to the primary location, configure it, load the latest data and start it.
It is also worth considering to analyse the possibility to run this one server system service directly from the secondary / backup site. Of course you should synchronise the updates of both (production) systems.
Spare systems are fully configured at the primary location and are waiting until they are activated after the failure of a production server system. There must be a good procedure to update the spare system as they cannot be online together with the production systems.
The fastest available deployable solutions are fault-tolerant systems. By building redundancy into systems (multiple power supplies, network cards, disk RAID levels, SAN) or building active-active clusters, the risk of loss of the server systems by failures can be significantly reduced. With this kind of solutions one should be alert for Single Point of Failures (SPoF) that impact the redundancy and fail a HA server system.
- A calamity mostly arises from an incident of external origin that expands across multiple hardware systems, software
systems or even employees. These incidents include:
Of course a failure can result in a calamity. For example, a server that is running too hot for a long time and reports
"overheating" as a failure can eventually result in a calamity such as a fire.
- Economic boycotts
- Software errors
- Storm damages
- Failing software updates
A cluster is a server system that is built using multiple servers in the same location that act as one server system and the service is offered in such a way that the user of the server system thinks he communicates with just one server system. Clusters are made up of nodes, each node is a server system. There are two types of clusters. The active-passive cluster has a node that handles the user requests, and the passive nodes monitors that the active node is still functioning properly. The active-active cluster has multiple active nodes that process the user requests. Of course, an active-active cluster should be configured that in case of failure the total processing power of the remaining nodes remains high enough to keep the users pleased.
- Computer Centre or room housing the systems that daily process and store information.
- Refer to primary location.
This term is interchangeable with the term "fail-over location". This is the location where the Business Continuity systems are prepared to take over the workload in case of a calamity.
- Server system:
Complete but limited combination of software and hardware to support a task for a user. For example: a file storage service consisting of a server with many hard drives and an operating system for file storage and an application for version-control.
In short: a failure is defined as a problem related to a program or a hardware component. Disturbances/failures can be solved with redundancy and high availability systems (HA)
- Refer: Secondary location.
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