Multi-AZ on COD
This section provides an overview on multiple availability zones and describes how COD ensures high availability and fault tolerance using Multi-AZ deployments.
To understand the Multi-AZ deployments on COD, it is important to know how AWS is configured across the globe and thus how it provides the redundancy of services regardless of your location. As discussed in Amazon’s official documentation, the AWS Cloud is made up of a number of regions, which are physical locations around the world. Each AWS region has multiple availability zones (AZs), which act as failure domains, preventing small outages from affecting entire regions. Most regions are home to two to three availability zones, with each AZ providing adequate redundancy within a given region. An AZ is represented by a region code followed by a letter identifier; for example, us-west-1a, us-west-1b.
However, this redundancy is only applied to the storage layer (S3) and does not exist for virtual machines used to build up your workload. If the availability zone where your server instances reside was having an outage, your services would cease to function, as the entire compute infrastructure would be offline.
A Multi-AZ deployment means that compute infrastructure for HBase’s master and region servers are distributed across multiple availability zones ensuring that when a single availability zone has an outage, only a portion of region servers will be impacted and clients will automatically switch over to the remaining servers in the available AZs. Similarly, the backup master (assuming the primary master was in the AZ having an outage) will automatically take over the role of the failing master since it is deployed in a separate AZ from the primary master server. All of this is automatic requiring no setup, no management, and no actions from a user or an administrative standpoint. It simply works to ensure an application does not suffer an outage due to the loss of a single AZ.
Cloudera has enabled the multiple availability zone based environments and workloads on AWS.
To understand more on the multi-az support on COD, refer to this Cloudera blog, High Availability (Multi-AZ) for CDP Operational Database.