How to leverage cloud architectures for high availability

Cloud architectures are used broadly nowadays; the cloud is a plethora of amazing alternatives in terms of services and solutions. However, with great power comes great responsibility, and the cloud presents itself as a place where failure can and eventually will occur. Thus, consequently, it will spread upon the entire architecture fast, possibly causing massive outages that can leave a business on its knees. Okay, that’s not an overly optimistic scenario – more likely the opposite – but not to fear. This is the nature of almost any architecture – and why should cloud be any different? Cloud architects face two different problems at scale at any given time in order to prepare for the worst; firstly, if something unexpected and undesired happens, how to continue business operations as if nothing happened, and secondly, if something unexpected and undesired happens and I am unable to continue operations as usual, how can I bring the architecture up someplace else and within a reasonable window of time, and then, resume operations as usual? In these terms we can discuss: Continue business as usual in the face of an outage. Resume business as usual in the shortest term possible in the face of an irrecuperable outage. The first is covered by high availability, and the second is covered by disaster recovery. Here, we will look at high availability. The alternatives currently on the table The cloud yields more than what is expected to face both scenarios. Most clouds are distributed in a geographic and technical way as to avoid massive outage scenarios by themselves; at a small scale, clouds have what is known as Availability Zones (AZs) or Availability Domains (ADs). These are usually different buildings, or different clusters of buildings, in the same geographic area, interconnected but highly redundant, especially in what refers to power, refrigeration and storage.