Most non-IT companies simply aren't designed to handle this level of complexity. AWS, however, takes care of all of these infrastructure requirements, allowing for a fault tolerant system without having to worry about the hardware itself.
Let's revisit our mobile banking app and see how it can be architected for fault tolerance. Currently, our mobile banking app has EC2 instances spanning multiple availability zones. The database has a read-only backup that is replicated once a day. This may be good enough for high availability, but fault tolerance sets a higher bar.
Instead of having a read-only database in another availability zone, an exact replica of the database would be housed there and possibly replicated to other regions. Every write operation to the database would essentially occur in parallel, ensuring the database is always up to date.
In a fault tolerant system, every aspect of the production environment's state is maintained in a partitioned system. That way it is always ready in case of a disaster. Instead of writing directly to the database, API requests are placed into a queue. This will mitigate possible deadlocks and timeout to the Database, thus reducing any possibilities of a single point of failure.
Remember that this, too, will have to be replicated in a separate environment to adhere to fault tolerance.
As you can imagine, having a replicated production environment can take significant time and resources to set up and maintain. However the cost-benefit analysis will be in the favor of a fault tolerant system if the business deems the system highly critical.
Whether or not to utilize high availability over fault tolerance depends on your budget, and consequently the importance of the system. If you are running an e-commerce website with millions of hits a day, a fault tolerant system is your best bet.
That being said, high availability might not cut it, and you will need to architect a fault tolerant website. If the system is running in a degraded state, there is a good chance that you will lose customers either way. So, you may as well up the budget to accommodate fault tolerance capabilities. On the other hand, let's say you are in charge of architecting a website for your employees, and it is not accessible from the internet.
It's only accessible from the company's intranet. In a situation like this, high availability would be perfectly acceptable. In the event that the database server goes down, it would crossover to a read-only database. After all, if your servers can survive downtime with DR goes beyond FT or HA and consists of a complete plan to recover critical business systems and normal operations in the event of a catastrophic disaster like a major weather event hurricane, flood, tornado, etc , a cyberattack, or any other cause of significant downtime.
HA is often a major component of DR, which can also consist of an entirely separate physical infrastructure site with a replacement for every critical infrastructure component, or at least as many as required to restore the most essential business functions.
A DR platform replicates your chosen systems and data to a separate cluster where it lies in storage. When downtime is detected, this system is turned on and your network paths are redirected. DR is generally a replacement for your entire data center, whether physical or virtual; as opposed to HA, which typically deals with faults in a single component like CPU or a single server rather than a complete failure of all IT infrastructure, which would occur in the case of a catastrophe.
A disaster recovery plan remains vital to business continuity strategy for many reasons. If your hypervisor system goes down with your servers, its HA functions may not work properly. You must configure your data storage to function with both the primary and redundant HA system. Data mirroring must work perfectly lest you end up with newly spun up servers and no or outdated data to populate their apps.
The data storage systems themselves must be set up as highly available, with no single point of failure. The interconnections between your HA systems must also function perfectly, so diverse connection paths and redundant network infrastructure is also required. While the majority of the time HA will work without a hitch, the chances of a problem rearing its head at some point in this complex stack becomes ever more likely the more you consider the elements at play.
HA can be expensive and difficult to configure and administrate , even when using a ready-made cloud solution. DR on the other hand is relatively inexpensive, as your stored systems can be configured to your desired RPO and RTO and you only pay for the storage rather than the running workloads. In HA and especially FT your backup servers must be ready to turn on at a moments notice so you are likely to incur charges for those resources on a constant basis.
With DR you only pay for the servers when they are spun up from a presumably geographically separate pool of compute resources. HA is a great fit for the most critical of applications and systems, the very backbone of your organization. Similarly to high availability, fault tolerance also works on the principle of redundancy. Such redundancy can be achieved through simultaneously running one application on two servers, which enables one server to be able to instantly take over another if one were to fail.
In virtualization, redundancy is achieved through keeping and running identical copies of a given virtual machine on a separate host. Any change or input that takes place on the primary VM is duplicated on a secondary VM. This way, in the event that the VM is corrupted, fault tolerance is ensured through the instant transfer of workloads from one VM to its copy.
Fault tolerant design is crucial to implement if your IT system cannot tolerate any downtime. If there are critical applications that support your business operations, and even a slightest downtime can translate into irrevocable losses, you should consider configuring your IT components with FT in mind.
A fault tolerant system is a system that includes two tightly coupled components that mirror each other, providing redundancy. This way, if a primary component goes down, the secondary one is always set and immediately ready to take over.
Disaster recovery involves a set of policies, tools and procedures to enable the recovery or continuation of vital technology infrastructure and systems following a natural or human-induced disaster.
Unlike high availability and fault tolerance, disaster recovery deals with catastrophic consequences that render entire IT infrastructures unavailable rather than single component failures. Since DR is both data- and technology-centric, its main objective is to recover data as well as get infrastructure components up and running within the shortest time frame after an unpredicted event.
Normally, DR requires having a secondary location where you can restore your critical data and workloads whether entirely or partially in order to resume sufficient business operation following a disruptive event.
To transfer the workloads to a remote location, it is necessary to incorporate a proper disaster recovery solution. High availability architecture is much more cost effective, but also bring with them the possibility of costly downtime , even if that downtime only lasts for a few moments.
Typically, fault tolerant systems are applied in industries or networks where server downtime is simply not acceptable. Any system that could potentially have an impact on human lives, such as manufacturing equipment or medical devices , will usually incorporate fault tolerant computing into its design. From a network IT standpoint, critical infrastructure may utilize fault tolerant systems because the solution makes sense for hardware and data center redundancies. Unfortunately, fault tolerant computing offers little protection against software failure, which is a major cause of downtime and data center outages for most organizations.
Most organizations are willing to accept the possibility of occasional downtime over the certainty of paying to implement a fault tolerant solution that may still be compromised by software problems. By implementing a wide range of strategies to provide backups and other redundancies, they can help customers get access to the applications and services they need with minimal disruption.
Ali is responsible for all engineering, construction, network, and information technology functions for the company. It could include a natural disaster that disrupts power and infrastructure, or a cyberattack that cripples their network systems.
Reliable networks are more important than ever, as businesses use them to access corporate and cloud resources. Users are constantly connected via mobile devices throughout the day and night.
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