Multi-AZ deployment on COD

How Multi-AZ deployment enables HBase high availability

To understand the Multi-AZ deployments on COD, it is important to know how a cloud provider is configured across the globe and how it provides the availability of services regardless of your location. A cloud provider is made up of a number of regions, which are physical locations around the world. Each 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 AZs, 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 AZ where your server instances reside is having an outage, your services cease to function, because the entire compute infrastructure is offline.

A Multi-AZ deployment means that compute infrastructure for HBase’s master and region servers are distributed across multiple AZs ensuring that when a single availability zone has an outage, only a portion of Region Servers is impacted and clients automatically switch over to the remaining servers in the available AZs. Similarly, the backup master (assuming the primary master was in the AZ, which is having an outage) automatically takes the role of the failing master because it is deployed in a separate AZ from the primary master server. The entire process is automatic and requires no setup and management from an user. Such a deployment works to ensure an application does not suffer an outage due to the loss of a single AZ.

To understand more on the Multi-AZ support on COD, see this blog, High Availability (Multi-AZ) for Cloudera Operational Database.