Thursday, March 31, 2016

AWS High Availability


http://docs.aws.amazon.com/AmazonElastiCache/latest/UserGuide/RegionsAndAZs.html
Regions are large and widely dispersed into separate geographic locations. Availability Zones are distinct locations within a region that are engineered to be isolated from failures in other Availability Zones and provide inexpensive, low latency network connectivity to other Availability Zones in the same region.
Important
Each region is completely independent. Any ElastiCache activity you initiate (for example, creating clusters) runs only in your current default region.
http://harish11g.blogspot.com/2012/06/aws-multi-region-high-availability.html
Architectures using Multiple AWS regions can be broadly classified into following categories:Cold, Warm, Hot Standby and Hot Active . 
In designing High Availability Architectures using Multiple AWS regions we need to address the following set of challenges:

  • Workload Migration - ability to migrate our application environment across AWS regions
  • Data Synch - ability to migrate real time copy of the data between the two or more regions
  • Network Flow - ability to enable flow of network traffic between two or more regions
The Following diagram illustrates a sample AWS Multi Region HA architecture.

Workload Migration: Amazon S3 or EBS backed AMI’s will operate only in regional scope inside AWS. We need to create the same AMI’s in another AWS  region again for inter region HA architectures. Every time when a code deployment is made, applications need to synchronize the executable /jars/configuration files across the AWS regions. Use of Automated deployments like Puppet, Chef will make things easier for such ongoing deployment cases.  Point to Note: In addition to AMI's ; Amazon EBS, ElasticIP’s etc also operate in AWS Regional scope.
Amazon Availability Zones are distinct physical locations having Low latency network connectivity between them inside the same region and are engineered to be insulated from failures from other AZ’s. They have Independent power, cooling, network and security. 

it is usually recommended to architect applications leveraging multiple availability zones of Amazon inside a region as best practice. Availability zones (AZs) are distinct geographical locations that are engineered to be insulated from failures in other AZs and come really handy during outages. By placing Amazon EC2 instances in multiple AZs, an application can be protected from failure or outages at a single location. 


It is important to run independent application stacks in more than one AZ, either in the same region or in another region, so that if one zone fails, the application in the other zone can continue to run. When we design such a system, we will need a good understanding of zone dependencies.

AWS offers infrastructure building blocks like 
  • Amazon S3 for Object and File storage
  • Amazon CloudFront for CDN
  • Amazon ELB for Load balancing
  • Amazon AutoScaling for Scaling out EC2 automatically
  • Amazon CloudWatch for Monitoring
  • Amazon SNS and SQS for Messaging
as Web Services which developers and Architects can use in their App Architecture. These building blocks are inherently fault tolerant, robust and scalable in nature. They are in built with Multi-AZ capability for High availability. Example: S3 is designed to provide 99.999999999% durability and 99.99% availability of objects over a given year. It is designed to sustain the concurrent loss of data in two facilities. Applications architected using these building blocks can leverage the experience of Amazon engineers for building highly available systems in the form of simple API calls.

https://aws.amazon.com/blogs/aws/elasticache-redis-multi-az/
The entire failover process, from detection to the resumption of normal caching behavior, will take several minutes. Your application’s caching tier should have a strategy (and some code!) to deal with a cache that is momentarily unavailable.


1 comment:

  1. Good info provided on the aws high availability, a complete info to get into the topic and its importance. Article is versed with the quality content and valuable information. thanks for sharing.

    ReplyDelete

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