High Availability
- 08 Aug 2024
- 1 Minute to read
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High Availability
- Updated on 08 Aug 2024
- 1 Minute to read
- Print
- DarkLight
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HA (High Availability) architecture ensures that your systems are up and running and accessible to your users in the face of unforeseen circumstances, such as hardware and software failures. HA does not guarantee that systems will not be hit by unplanned interruptions.
High Availability involves setting up redundant systems, at least two Application Servers, and a Load Balancer. The primary goal is to eliminate any single points of failure within a process or system. Redundancy ensures that if one server fails, another immediately takes over, maintaining seamless operations without disruption.
How to Attain High Availability
The ideal HA architecture should include elements to ensure redundancy, data backup and recovery, automatic failover, and load balancing.
Server Redundancy
This model adds an independent server to your hosted infrastructure. It can be active/passive, meaning that the backup server is on standby and ready to take over when a main server goes down, or active/active, meaning the backup servers are running simultaneously with the main server. Although this is the least costly model, it is not entirely redundant. Thus, it may not be entirely suitable for large systems.
Geographic redundancy
This model distributes the servers across multiple locations. When a location goes down, another site takes over, keeping your operations running. Given its costs, hosting the application on a cloud services provider with data centers worldwide is the best option.
Data Backup and Recovery
Full data backups are required to ensure HA and should be included in the disaster recovery planning. Replicate your data by storing them in secondary servers or standby instances across multiple locations. The data in these locations should always be synchronized with the data in your primary location. The other locations should be ready to take over when disaster strikes your primary location.
Load Balancing
HA architecture ensures better and more reliable application performance using load balancing, a process that involves distributing network traffic across multiple servers using either a hardware- or software-based solution.
Uptime SLA chart
SLA | Downtime per week | Downtime per month | Downtime per year |
|---|---|---|---|
99% | 1.68 hours | 7.2 hours | 3.65 days |
99.9% | 10.1 minutes | 43.2 minutes | 8.76 hours |
99.95% | 5 minutes | 21.3 minutes | 4.38 hours |
99.99% | 1.01 minutes | 4.32 minutes | 52.56 minutes |
99.999% | 6 seconds | 25.9 seconds | 5.26 minutes |
Deployment configuration for all the different uptime SLA
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