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Fault tolerance has now become a core requirement, not an optional extra. Businesses need to keep their apps or services available 24/7 in order to meet customer and stakeholder expectations and remain profitable.
Otherwise, unavailability frustrates customers, leading to reduced customer satisfaction, which ultimately decreases revenue.
Amazon Web Services (AWS) has quickly become one of the go-to cloud platforms with over 200 fully featured services such as AWS EC2, Lambda, S3, DynamoDB and RDS; millions of active users; and an unparalleled high availability feature set allowing developers to build fault-tolerant business apps quickly with minimal interaction or investment needed from AWS high availability features.
This guide is intended to introduce how to achieve high availability in AWS.
We discuss its fundamental concepts, high availability architecture and benefits, as well as provide an in-depth examination of computing and database storage capabilities. Note that Multi-Availability Zones (AZs) deployment isn't supported for read-only instances. Therefore, you should utilize read replicas in order to ensure high availability.
What Is High Availability?
Highly available systems remain functional even if critical components fail, providing resilience against failure without disrupting services or losing data, as well as recovering quickly when disasters strike.
High availability can typically be measured as a percentage of uptime; "nines" is commonly used as an indication that systems have reached this level; four nines indicate they've reached 99.99% uptime - that means only 52.6 minutes were lost annually.
The following components help you implement highly available systems:
- Redundancy involves providing critical system components with duplicate copies with similar data, so in case one component should fail, the other can take over immediately and seamlessly.
- Monitoring involves identifying issues in production systems that might interfere with service provisioning or otherwise disrupt it.
- Failover refers to the ability for active system components to switch off or over to redundant ones in case of failure, impending failure, reduced performance or functionality or diminished functionality; failback--when they recover--enables switching back.
AWS High Availability For Compute, Databases, And Storage
What is high availability in AWS? AWS enables you to achieve high availability for cloud workloads in three distinct dimensions:
- Amazon EC2 and other computing services from AWS feature high availability features like load balancing, autoscaling and provisioning across Availability Zones (AZs).
An Availability Zone is an isolated section within an Amazon data center where processes may take place without interference from external influences.
- Amazon RDS and similarly managed SQL databases allow for the automatic deployment of databases with standby replicas in separate AZs, providing quick deployment.
Amazon Storage services such as S3, EFS, and EBS all include high-availability features built right in. S3 and EFS automatically store data across multiple availability zones (AZs), while EBS allows snapshot deployment in multiple AZs.
AWS Provides High Availability For EC2 Instances.
Amazon EC2 instances feature various built-in features designed to ensure high availability:
- Elastic Load Balancing allows you to launch multiple EC2 instances and distribute traffic between them.
- Availability Zones—you can place instances in multiple AZs.
- Auto Scaling—auto-scaling detects when loads increase and dynamically adds new instances.
These capabilities are illustrated in the diagram below.The Elastic Load Balancer routes traffic between two or more EC2 instances, each of which may be deployed in a separate subnet in a different Amazon Availability Zone.
These instances can be part of an Auto-Scaling Group, with additional instances launched on demand.
Read More: Maximizing Tech Monitoring with AWS: What's the Cost of Inaction?
AWS High Availability For SQL Databases On Amazon Rds.
If your AWS app requires SQL databases, Amazon RDS multi-AZ likely provides high availability through Multi-Availability Zone deployments.
In these deployments, RDS automatically creates a replica database instance within each availability zone in case one goes down; users are seamlessly transferred back when that instance fails - without losing functionality altogether. This creates two levels of redundancy.
- In case the active database fails, a standby replica is ready to receive requests.
- If your main database instance experiences a disruption in one AZ, it will fail over to another.
Enabling this feature requires choosing "Multi-AZ Deployment" when creating an RDS database instance using either the RDS Console or Amazon CLI, with no administrative intervention necessary.
These multi-AZ deployments operate autonomously with no need for administrative intervention on your part.
AWS Storage Services Provides High Availability
Here's a brief run-down on Amazon's high availability features for other popular storage services:
- Amazon S3: Amazon S3 ensures 99.999999999% durability by redundantly storing objects across at least three devices across an Amazon S3 Region.
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Amazon EFS: EFS guarantees 99.9% availability; otherwise, between 10%-10% of its service fee may be reduced accordingly.
Every file system object is stored redundantly across different AZs to meet this guarantee.
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Amazon EBS: EBS volumes are created within one Availability Zone (AZ).
You can make them accessible in another AZ by attaching them to instances within that AZ, creating snapshots, restoring them elsewhere within that same region or copying snapshots across AWS regions for redundancy purposes.
Benefits Of Using AWS High Availability For Web Applications:
High availability on AWS for web applications offers several key benefits:
- AWS HA provides a secure network that features Web Application Firewall (WAF) protection to stop common web exploits and includes features like Business Continuity (BC) and Disaster Recovery (DR) capabilities that help business requirements for regain operations as soon as possible after any disruption in service occurs.
- As soon as a sudden hardware failure happens or threatens to happen, AWS Auto Scaling detects it and launches a replacement instance.
- AWS HA provides cloud metrics so administrators can closely track application usage based on factors like the number of users or memory consumption by each instance.
- New features or updates can be implemented seamlessly without creating problems for existing users.
AWS Regions And High Availability Zones
- Amazon Web Services (AWS) services are hosted across multiple AWS locations, each one offering multiple availability zones that have an uptime range from 99.99% to 99.999%.
- Each AWS Region operates completely autonomously to offer maximum fault tolerance and stability for user and application workloads.
- All Amazon Web Services Availability Zones (AZs) are created with one goal in mind - low latency network connectivity between them in their region, linked by various Internet Service Providers (ISPs) or power grids.
- By spreading out EC2 instances across various Availability Zones, you can safeguard against failure in one data center and protect your applications(s).
- Operating multiple independent application stacks across various Availability Zones in different regions or even within one is key to ensuring continuity if one area experiences issues and another does not fail altogether.
If one application availability should fail, its functionality will continue as planned while functioning normally in another zone.
Ensure High Availability In AWS With Cloud Volumes ONTAP
CISIN Cloud Volumes ONTAP, an enterprise-grade storage management solution, provides secure and dependable storage management services on AWS, Azure and Google Cloud platforms.
The software-only service features data control alongside enterprise-class storage features like high availability data protection file sharing efficiency as well as integration of Kubernetes integration.
Cloud Volumes ONTAP allows customers to take advantage of data protection and high availability while remaining non-disruptive to operations and mitigating risks.
When configured in High Availability mode, customers are assured of business continuity through zero data loss (RPO=0) and short recovery times (RTO=60 secs).
Cloud Volumes ONTAP's high availability ensures your application server runs seamlessly 24/7, from its dual node configuration with synchronous replication ensuring 100% data integrity, resulting in zero RPO and RTO times of less than 60 seconds.
Conclusion
As this blog post has demonstrated, AWS high availability best practices offers fault-tolerant systems.
You have gained insight into the wide array of computer, database server and storage services available through AWS. Each offers solutions designed to prevent degradation or points of failure, while AWS's low costs allow minimal human involvement and initial financial investment, making it the optimal platform for developing fault-tolerant software systems.
