On a public service demands that always ready in 24 hours, needed a high availability management that make sure system is always running. Therefore, if we want to  create a system with a high level of availability is not as easy and simple as installing a piece of software and hardware, or using not just run a command periodically with a syntax xxx –full-online.

If we want to build system with high availability,  it’s needed best platform and system to make sure public service always running anytime from node to node. Analyze and performance test of each element, constructing and testing an end-to-end solution that encompasses people, process, and technology is the only tried-and-true method of preparing for a potential disaster. Redundant technology for availability only provides the end physical manifestation of a larger, agreed-on goal that also takes into account security and performance.

High availability is a system design protocol and associated implementation that ensures a certain absolute degree of operational continuity during a given measurement period. There are two main aspects to consider when thinking about high availability, prevention and disaster recovery. Prevention is anything—including people, processes, and technology—that, when put in place, is designed to reduce the risk of a catastrophic occurrence. The harsh reality is that, despite planning, failures can occur. Disaster recovery is the process, policies and procedures related to preparing for recovery or continuation of technology infrastructure critical in order that system always running after a natural or human-induced disaster.

How do calculate the level of system availability ?  Availability is usually expressed as a percentage of uptime in a given year. The following table shows the downtime that will be allowed for a particular percentage of availability, presuming that the system is required to operate continuously.

           Availability = ((total units of time - downtime) / total units of time) x 100%

 

for example 

1. Total units of time : 8760 hour

2. downtime system : 8 hour

3. availability = ((8760 - 8)/8760) x 100%

4. result = 0.999 x 100% = 99,9 %

 

The calculation example yielded a result of 99.9 percent uptime. This equates to three nines of availability, but what exactly is a nine? A nine is the total number of consecutive nines in the percentage calculation for uptime, starting from the leftmost digit, and is usually measured up to five nines. See detail secret of number nine at this picture.

 

Percentage calculation and Number Nine

Percentage calculation and Number Nine

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