AWS Fault Tolerance and High Availability

Amazon Web Services provides the services and infrastructure to build highly available and fault tolerant environments in the cloud. However, like most clouds, you have to design your systems for fault tolerance and high availability by utilizing the services offered by AWS.

Some AWS services have already been designed by Amazon to be highly available and fault tolerant. These include Amazon Simple Storage Service (S3), Amazon Simple DB, Amazon Simple Queue Service (SQS), and Amazon Elastic Load Balancing (ELB).

Most companies who build their infrastucture in AWS will use Amazon Elastic Compute Cloud (EC2) and Amazon Elastic Block Store (EBS) for their virtual servers (EC2 instances), and disk storage for their servers (EBS volumes). These virtual servers live on physical hosts, and these EBS volumes live on physical disks. Physical hosts have power supplies, motherboards, and RAM which can and will die. Physical disks can and will fail.

While AWS would have set up RAID for their drives and fail over clustering for their hosts, anyone wanting to create an infrastructure in the AWS Cloud (or any other cloud provider for that matter), will need to design high availability and fault tolerance into the services that they are offering.

AWS has features such as availability zones, elastic IP addresses, and snapshots which the cloud architect can utilize to implement high availability and fault tolerance for their virtual server environments.

Just moving a system into the cloud doesn't make it fault tolerant or highly available.

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