What is High Availability?
High Availability, or HA, refers to the objective and associated strategies to maintain system uptime and accessibility against threats of unexpected performance and system failure, for many businesses it is essential to operate highly available systems. As one of the leading companies offering highly available software, discover in depth how our highly available solutions and services can help your business operations.
The system may consist of any number of key dependencies including hardware components, utilities, software and access points, all of which must be maintained to ensure system integrity and user availability. The failure of any single dependency may threaten the service viability of the entire system resulting in system downtime.
What is system uptime or downtime?
Downtime describes the actual time a system is unavailable and includes the time to recover from unexpected failures as well as planned maintenance time windows.
Conversely, system uptime represents the time a system has been fully operational as a percentage of total potential time availability and is often described by a number of nines. Three nines for example refers to 99.9%, which when taken over a calendar year, represents approximately one business day or 8.5 hours. Four nines (99.99%) over a year represents just under an hour, and five nines (99.999%) only five minutes. To achieve five nine service availability therefore requires building, designing, maintaining, and running a system that will remain completely operational with planned maintenance windows for all but just five minutes across a calendar year.
What uptime can be achieved without High Availability software?
There are many examples of systems that have run beyond a year without any high availability capability that have provided 100% uptime capability. By architecting optimal system design practice, using high quality enterprise-grade components with low failure rates and using robust and comprehensive operational procedures, it is possible to significantly reduce the likelihood of failure, but this approach alone also requires considerable luck.
What are the main benefits of a highly available system?
- Protection of business revenues and data assets
- Enhanced service uptime
- Automatic and predictable recovery from failure
- Non-disruptive system upgrade capability
- Failover "fire drill” testing
Find out how to set up the HA configuration and FAQ’s on high availability clusters.
Why is High Availability important?
As there is almost always a financial element associated with system downtime, whether through loss of direct revenue, productivity, reputation, or consequential loss, ensuring key systems operate with a high level of availability and accessibility is critical.
As most IT service contracts are governed by Service Level Agreements (SLAs) including provisions for server uptime, service availability guarantees and penalties, it is important to design, build and run systems that operate within the prescribed service availability requirements. Enhancing system High Availability is therefore not just aspirational but absolutely essential.
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