The term pilot light is often used to describe a Disaster Recovery scenario in which a minimal
version of an environment is always running in the cloud. The idea of the pilot light is an analogy
that comes from the gas heater. In a gas heater, a small flame that’s always on can quickly ignite the
entire furnace to heat up a house.
With AWS you can
maintain a pilot light by configuring and running the most critical core elements of your system in
AWS. When the time comes for recovery, you can rapidly provision a full–scale production
environment around the critical core.
The pilot light method gives you a low cost option for DR since you only pay for the pilot light resources
during normal operations, and only pay for all resources required to run your operation
during a DR event.
Infrastructure elements for the pilot light itself typically include your database servers, which
would replicate data to Amazon EC2 or Amazon RDS.
Depending on the system, there might be other
critical data outside of the database that needs to be replicated to AWS. This is the critical
core of the system (the pilot light) around which all other infrastructure pieces in
AWS (the rest of the furnace) can quickly be provisioned to restore the complete system.
To provision the remainder of the infrastructure to restore business–critical services, you would
typically have some pre–configured servers bundled as Amazon Machine Images (AMIs),
ready to be started up at a moment’s notice. When starting recovery, instances from these AMIs
come up quickly with their pre–defined role (for example, Web or App Server) within the deployment
around the pilot light.
The pilot light method gives you a quicker recovery time than the backup/restore method
because the core pieces of the system are already running and are continually kept up to date.
enables you to automate the provisioning and configuration of the infrastructure resources, which can be a
significant benefit to save time and help protect against human errors. However, you will still need
to perform some installation and configuration tasks to recover the applications fully. These
configuration steps may be automated with AWS CloudFormation
Recovery to the Pilot Light environment entails spinning up pre–configured systems from
AWS AMI images, applying any patches not previoiusly applied and making the replicated data available to new systems.
Network addressing is then changed via Amazon Route 53 to point to the new instances