In this article, we are going to discuss on what is High Availability and Disaster Recovery in general.
- High Availability
- Disaster Recovery
What is High Availability:
- In the perfect world, the data should be available no matter what. But, in the real world there are many problems that can cause the data to become unavailable.
- One of the most important goals for the mission critical applications is ensuring the data is always available. To achieve this, we need to have proactive approach/Strategy.
- The main goal of high availability (HA) is to minimize and mitigate the impact of downtime to end users and maximize availability. High availability solutions aim to mask the effects of failures( hardware, software) or natural disasters and have the critical data available as soon as possible in the event of a failure or disaster.
What are the pillars:
High availability is about putting together people, processes, and technologies in place before a failure occurs to prevent the failure from affecting the availability of the data. Most often, people and processes are forgotten, and technology is given the most importance. It should be the other way around as most downtime’s are caused due to people and process issues. To achieve high availability, you need support from all three pillars: people, process, and technology.
Causes of Downtime:
There are mainly two types of downtime:
- Planned downtime
- Unplanned downtime
Unplanned downtime not only will make the data unavailable but in many cases may also cause data loss. In most cases, data loss can be prevented or minimized by investing in planning for such events in advance .
Disaster recovery is about using people, processes, and technologies to recover any lost data and make it available again after a failure occurs.Many customers use high availability and disaster recovery interchangeably because it is possible to have a solution that provides both high availability and disaster recovery. However, it is not necessary that if a solution provides high availability, it will also provide disaster recovery and vice versa. In fact, it is common to see most of our customers have some form of high availability. However, disaster recovery is mostly on their to-do project list, which is often never implemented and paid attention to until a disaster actually occurs.
Recovery Time Objective ( RTO ): It is the maximum allowable downtime when a failure occurs.
Recovery Point Objective ( RPO ) : It is the maximum acceptable level of data loss after a failure occurs.
Recovery Level Objective ( RLO ): It defines the granularity with which the data needs to be recovered after a failure occurs. For an SQL Server, it will define whether you must be able to recover the whole instance or database or a group of databases or tables.
In this article, we have explored High availability and Disaster recovery, pillars to build high available solution and the causes for downtime, how to recover from a disaster.