Many of you are familiar with the concept that time is money. The bottom line will suffer for every minute a product is not created, advertised, and sold. This concept is vital in IT. Every second a system is down means that revenue and productivity are affected. It is estimated that 98% lose $100,000 every hour that a system goes down. That’s quite a sum.
AWS allows teams to build resilient web applications that are virtually indestructible. They simply need to ensure that their systems are either highly available or fault-tolerant. Both of these are disaster recovery methods.
It takes time and resources in order to ensure that your systems are resilient. But that is nothing compared to the potential losses that can be incurred from downtime. It is therefore crucial that your system is highly available and fault-tolerant. Let’s find out how they work and what makes them different.
What is High Availability?
High availability means that the system will almost always be available, even if it is in a compromised state. AWS is defined as having 99.999% uptime. Also known as the “five nines”, this means that a system is high-availability. This means that the system would only be down for five minutes and fifteen seconds per year. Yes, it is possible and even common for AWS.
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Start trainingHigh availability can be achieved by removing single points for failure using system redundancy. If you had five computers connected directly to one server, this would be a single point for failure. If the server room floods and destroys the server, you are out of luck.
A backup server can be turned on to protect against this possibility. This is adding redundancy in order to eliminate single points of failure. Redundancy is an additional way to remove single points of failure.
This was a costly and difficult situation to maintain in pre-AWS times. This was usually done by configuring complex RAIDs in order to ensure database redundancy. Hardware would also need to be stored in expensive, temperature-controlled, bomb-shelter-like structures.
High availability has become a feasible option for almost any organization due to the abundance of cloud services. Let’s dive deep into how AWS can be used to eliminate single points or failures and maximize redundancy.
Example: A Mobile Banking App
Let’s suppose that you are responsible for creating a mobile banking application. The app would allow users to view their account balances, make transfers and withdraw funds. The ideal scenario is that the app should allow the user to perform all three operations at once. In the real world, however, something will fail. This is where high availability architecture comes into play.
Servers for our banking app will be available in multiple availability zones to ensure high availability. Multiple servers can be configured in the same way within these availability zones. AWS servers are commonly referred to as EC2 instances. This means that if one availability area goes down, the mobile application will point to the backup availability zone. This will eliminate any single point for failure.
What about user data? You must back up your user data. It is part of a redundant system that ensures that the primary data is being replicated on a separate database with read-only access. Users will still be able view their account balances if the primary availability zone is down. They will not be able to withdraw funds or transfer funds. This is because these are write operations and the backup database was only created for read operations.
High availability does not guarantee full functionality, but essential services. It is important to remind people that they can access essential services once or twice per year.
