High Availability Architecture

Following points can be considered while creating a highly available architecture depending on scenarios
  •  A spread Placement group Supports a maximum of seven running Instances per availability zone.for example, In A region with three Availability zones, you can run total of 21 instances in the group.If you try to start an eighth Instance in the same availability zone and in the same spread placement group, the Instance will not launch.If you need to have more than seven instances in an availability zone,Then the Recommendation is to use multiple spread Placement Groups. Using multiple spread Placement Groups does not provide guarantee about the spread of instance between groups, but it does ensure the spread for each group, thus limiting impact from certain classes of failures.
  • Durability refers to the ongoing existence of the object or resource. Note that it does not mean you can access it, only that it continues to exist.
  • Groups, Scaling options, configuration templates are components of amazing EC2 autoscaling.
  • In the event of a planned or unplanned outage of your DB Instance, Amazon RDS automatically switch is To a standby Replica in another availability zone if you have enabled multi–AZ. You can force a fail over manually when you reboot a DB instance.
  • You can’t use the standby(secondary database) To offload reads from an application. The standby Instance is only there for failover. If you want an independent read node, you need to create a special type of DB Instance called a read replica, from a source DB Instance.
  • Availability can be described as the percentage of a time period When the service will be able to respond to your request in some fashion.
  • Resiliency is the ability of a Workload to recover from infrastructure or service descriptions, dynamically acquire computing resources to meet demand, and mitigate disruptions, such as misconfigurations or transient Network issues.
  • Reliability is closely related to Availability, However a System can be available but not be working properly. Reliability is the probability That system will work as designed.
  • Scaling out is where you have more off the same resource separately working in parallel (visualize services setting side by side). Scaling up is where you make it 
    bigger and bigger like an ugly tower with more floors being added after the initial design was finished.
    S3 Standard, S3 Intelligent-Tiering, S3 Standard-IA, S3 One Zone-IA, S3 Glacier, and S3 Glacier Deep Archive Amazon S3 storage classes, objects are designed for 99.999999999% (11 9’s) durability
  • EC2 Autoscaling works in conjunction with the AWS Autoscaling service to provide a predictive ability to your autoscaling groups.

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