High Availability solutions overview
High Availability is the high degree of accessibility and functionality of a service or application. It is measured based on user perception and defined by terms like reliability, recoverability, error detection and continuous operation.
Reliability – Having reliable hardware equipment is an important part of any high availability solutions, just like having functional software applications, databases, web servers, email servers, file servers and so on.
Recoverability – There could be many possible solutions for recovery from a critical situation. It is very important for any business to identify critical situations and their recovery solutions, so that none of the key business processes are affected.
Error detection – The implementation of a recovery plan requires a mechanism for monitoring and detection of possible malfunctions in case a key component of the IT infrastructure becomes inoperable. The mere existence of a recovery plan is useless without continuous monitoring and reporting procedures that trigger each stage of the recovery plan.
Continuous operations – Continuous operations are essential to any successful company; that means maintenance activities for infrastructure should be transparent to users and business processes. For the maximum acceptable disruption (downtime) of a service or application to tend to reach zero, any operation such as relocating equipment or replacing any hardware unit should be transparent to users and not affect business processes.
The importance of a High Availability solution
The importance of a High Availability solution can vary from business to business. However, what is generally true is that successful organizations tend to accelerate business processes by redesigning their IT infrastructure in order to gain a high competitive advantage.
This trend generates a need for solutions that ensure availability and access to information so that the business processes operate at highest functionality and without downtime.
Downtime causes lack of productivity, it deteriorates business relations, generates financial losses and negative publicity.
It is not always easy to estimate the real cost of resulting downtime. If an interruption of a critical service or application is less than 30 seconds, the impact is usually acceptable, even negligible, but as downtime increases, the effect of a minor problem can become a major one, leading to high financial losses.
Many companies choose to protect themselves against critical situations with insurance policies, when a High Availability solution is, in fact, the most competitive policy.
Implementation of High Availability solution
The nature of global businesses has created a necessity for High Availability solutions for various business components. However, organizations that implement a High Availability strategy have to conduct a thorough analysis of all key components of the business to know what equipment they need to discard, what systems and solutions they need to invest in, how to rebuild the entire IT architecture according to the implemented HA model and how to redefine business processes.
With higher availability, downtime is reduced according to the table below:
An organization with increased High Availability requirements should choose fault-tolerant (redundant) equipment and solutions to ensure that the risk of downtime is minimized.
To find viable High Availability solutions o thorough analysis must be made consisting of: Business Impact Analysis, Cost of Downtime, Recovery Time Objective and Recovery Point Objective.
The fact that business processes within an organization are divided by level of criticality should be taken into consideration.
Two other important aspects in achieving a High Availability strategy are: estimating future business growth and scalability of existing architecture.