This blog was updated August of 2021 to provide more useful information to our readers. We hope you enjoy! If you have any questions, please do not hesitate to reach out to us!
The critical nature of today’s cloud workloads has made choosing the right cloud architecture more important than ever. To reduce the potential for system failures and hold downtime to a minimum, building your cloud environment on high availability cloud architecture is a smart approach, particularly for critical business applications and workloads. There are several reasons why this approach ensures high uptime. By following the current industry best practices for building a high availability cloud architecture, you reduce or eliminate threats to your productivity and profitability.
Many businesses face a decision: do you keep your systems at the 99.99% level or better? If so, you must design your system with redundancy and high availability in mind. Otherwise, you may face a lesser service level agreement where disaster recovery or standby systems are enough, but that comes with the potential risk of your website crashing.
How High Availability Cloud Architecture Works
High availability is a design approach that configures modules, components, and services within a system in a way that helps ensure optimal reliability and performance, even under high workload demands. To ensure your design meets the requirements of a high availability system, its components and supporting infrastructure require strategic design and testing.
While high availability can provide improved reliability, it typically comes at a higher cost. Therefore, you must consider whether the increased resilience and improved reliability are worth the larger investment that goes along with it. Choosing the right design approach often involves tradeoffs and careful balancing of competing priorities to achieve the required performance.
However, in the end, the improved reliability often prevents network downtime and the loss of productivity that comes with it. The costs associated with this downtime may quickly add up to more than the initial investment. Luckily, the higher costs associated with building a high availability architecture may pay for themselves more quickly than you might think.
Although there are no hard rules for implementing a high availability cloud architecture, there are several best practice measures that can help ensure you reap the maximum return on your infrastructure investment.
Why Do You Need High Availability Cloud Architecture?
High availability cloud architecture protects against three major issues: server failure, zone failure, and cloud failure. It also allows you to automate and test everything in your network. While the last feature is useful, this type of cloud network architecture is mainly used to prevent failures and reduce downtime.
Protects Against Server Failure
Server failure is more of a “when” situation than an “if” situation. Servers are eventually going to fail due to age, if nothing else. Preparing for server failures is a must, no matter what type of cloud architecture you use. High availability cloud architecture protects against server failure by making use of automated balancing of workloads across multiple servers, networks, or clusters.
Auto-scaling will allow your system to monitor active traffic in real-time. It uses various metrics to determine the overall load on each server and shift that load as necessary to prevent one server from becoming overworked. Should a server fail, the system will shift all users to another server seamlessly.
In addition to traffic monitoring and shifting, high availability cloud architecture also mirrors databases to ensure that information is available from more than a single source. This architecture also uses static IP addresses and dynamic DNS to reduce downtimes.
Protects Against Zone Failure
Zone failure occurs when an entire server farm or zone fails. This occurs when there is a massive power failure, natural disaster, or network outage that takes down backups as well as primary power sources and network connections. The result is that an entire zone of servers becomes unreachable.
High availability cloud architecture addresses this zone failure by spreading its servers across multiple zones. The architecture replicates data and databases across zones. If one zone fails, there is at least one other zone the system can route users to without losing access to any applications or data. Typically, these zones are not physically near each other. One server cluster may be in Europe, while another is located in North America. This helps avoid issues where a single natural disaster could affect both zones at once.
Protects Against Cloud Failure
While it is rare for two zones to fail, there is always the risk that this will occur. Total cloud failure, while rare, can happen. To handle such an outage, high availability cloud architecture requires modules that can be moved and used across different providers and infrastructures. By creating and storing data backups across providers or regions, it is possible to quickly restore access to this information. This may only be regional access, but it is still a way to retrieve data when the cloud is unavailable.
Another way high availability cloud architecture prepares for cloud failure is by creating sufficient storage space and server capability to absorb the loss of a zone or the entire cloud. You may not need to use these reserve servers and backup drives often, but they are available in case of a large-scale disaster.
Automate and Test Everything in Your Network
In addition to providing backup for server, zone, and total cloud failures, high availability cloud architecture automates processes and allows for full testing of those processes. For example, you can simulate a server, zone, or cloud failure at any time to watch how your system reacts. This allows you to create processes to save and restore data, automatically adjust workloads, and much more.
By automating processes, you ensure that your disaster recovery plan is implemented immediately. These processes back up your data regularly, ensuring you always have the latest information available. The system immediately detects problems, moves users away from the identified servers, and sends out maintenance alerts as needed.
Testing your plan allows you to make certain it works exactly as intended. High-level cloud disasters can cripple a business, so testing is mandatory to avoid downtime. By running multiple tests, you can detect your architecture’s weak areas and take steps to improve them.
What Goes into Building a High Availability Cloud Architecture?
Creating a high availability cloud architecture begins with design. Many may assume that the more redundant systems and backups you have, the more stable the system is. However, that’s not always the case. In fact, too many components can create a very complex system that does not operate effectively or efficiently. The key is to optimize resources, minimize response times, and prevent one part of the system from becoming overloaded.
Here are some of the components of a high availability cloud architecture that you will need to build, maintain, and scale your system:
Multiple Application Servers
The first step to building a cloud architecture is to make use of multiple servers or server zones. These zones ensure that your user load is distributed so that no single server is overloaded. It also allows for backup servers and redundancy.
You will need to design your databases to scale from the onset. You will also want to create backups of these databases on a very regular basis. Every database should have a backup that exists on another server, and ideally, in another geographical location.
Recurring Automated Backups
Automatic backups reduce the chance of human error and prevent data loss. You will want to determine the exact timing of these backups based on how often new data is introduced to your database. In some instances, you may need to have your databases backed up in real-time.
Requirements of High Availability Cloud Architecture
There are four main requirements for high availability cloud architecture.
More efficient workload distribution helps optimize resources and increases application availability. When the system detects server failure, it automatically redistributed workloads to servers or other resources that continue to operate. Load balancing not only helps improve availability, but it also helps provide incremental scalability and supports increased levels of fault tolerance.
Overall, automatically rebalancing of workloads seamlessly shifts users to other servers when one fails. This rebalancing also means there is less strain on a server, meaning there is less risk of unexpected failure.
A cloud architecture that cannot scale up or down as needed is ineffective. Your architecture needs to be easily scalable. You can achieve this in several ways. Users can access a centralized database. The server housing this database needs to be able to handle a large number of requests, especially if you expect your business to grow soon. Having at least one backup for this database is also vital. Another option is to allow every application instance to maintain its own data. The system will need to regularly sync this data with other applications or servers to ensure that all users have the same information.
As mentioned earlier, a high availability cloud architecture requires servers located in at least two geographical locations to avoid failure from losing one server zone. While having two locations is the minimum, ideally you will have servers located in three or more.
Recovery and Continuity Plans
The fourth key element of a high availability cloud architecture is a backup and recovery plan. While backup servers and databases combined with different geographical locations can greatly decrease the risk of failure, that risk is never going to be zero. Having a backup and recovery plan is necessary to reduce downtime.
Your business continuity and recovery plan should be well-documented and regularly tested to ensure it’s still viable. You should provide in-house training on recovery practices to help improve internal technical skills in designing, deploying, and maintaining high availability architectures. Additionally, well-defined security policies can help curb incidences of system outages due to security breaches.
You will also need to define the roles and responsibilities of support staff. If you must move to a secondary data center, how will you effectively manage your cloud environment? Will your staff be able to work remotely if the primary office or data center location is compromised? In addition to the hardware and infrastructure, the fundamental business continuity logistics and procedures are an important part of your high availability cloud design.
Types of Cloud Clusters
There are three different types of high availability cloud architecture. Each of these concepts has its pros and cons. However, by planning out your server cluster in advance, you reduce your risks of failure and keep your data, along with your server, much safer.
In this type of cluster, the system recognizes when the active server fails and automatically transfers the user to another server at the same location. The system automatically sets the IP address of the failed server to standby and alerts the system operator of the issue.
In this model, the user works on the active server only. When that server fails, the system moves them to the passive or backup server. The system shifts the load to the backup server, making it the active server and chooses another as the passive or backup.
Active/active cluster is the second type of cloud cluster. In this model, there are at least two servers with the exact same configuration. Users access both servers, and the system attempts to keep the workload evenly distributed between the two. When a server fails, it automatically shifts all users to the other server. When the failed server is repaired or replaced, the system balances users between the two again.
In this model, there are no true backup servers like there are in the Active/Passive model. All servers are regularly in use. This means you have more servers to distribute the workload. However, on the downside, when one server fails, its paired server takes on its users. This doubles the number of users accessing that server’s resources and can cause some issues.
Note that it is possible to run both active/active and active/passive models on the same cloud architecture. Adding a single passive backup server allows the system to bring that server in to replace a failed active server. One server is always out of rotation, making it easier to schedule maintenance time. Should multiple servers fail, the passive server will step in for one, while the others will take on additional users until the servers are repaired or replaced.
Shared vs Not Shared
Shared vs not shared is the third model. This cluster concept is based on the idea that there should always be redundant or replacement resources available. One failure should never result in loss of service. For example, if there are multiple nodes that need to access a single database, that database becomes a point of failure. This shared cluster presents a risk of losing productivity should the server hosting the database fail.
A system that does not share resources, sometimes called a shared-nothing cluster, does not have a single point of failure. Instead, every server has its own database. These databases are synced and updated in real-time, so all data is consistent across the node. One server failure will not affect the other servers.
High availability cloud architecture must avoid single points of failure. One of the best ways of ensuring 99.99% uptime is to combine the active/active and active/passive concepts as mentioned above. Combine this with a shared-nothing approach to databases and other resources to eliminate single points of failure. The result will be a highly redundant system that will only fail in very extreme circumstances.
Best Practices for a Cloud Architecture
There are several different best practices you can make use of when implementing high availability cloud architecture. They each have amazing benefits that can help you do more with your business when used properly.
Upfront Load Balancers:
With network load balancers installed in front of servers or applications, traffic or users will be routed to multiple servers, improving network performance by splitting the workload across all available servers. The load balancer will analyze certain parameters before distributing the load, check the applications that need to be served, as well as update the status of your corporate network. Some load balancers will also check the health of your servers, using specific algorithms to find the best server for a particular workload. By doing so, no single server is put under unnecessary strain.
Should a system failure occur, clustering can provide instant recovery by drawing on resources from additional servers. If the primary server fails, a secondary server takes over. High availability clusters include several nodes that exchange data using shared memory grids.
The benefit here is that should any server or zone be shut down or disconnected from the network, the remaining cluster will continue operating as long as one node is fully functioning. Individual nodes can be upgraded as needed and reintegrated while the cluster continues to run.
The additional cost of implementing extra hardware to build a cluster can be offset by creating a virtualized cluster that uses the available hardware resources. For best results, you should deploy clustered servers that share storage and applications. Each should be able to take over for one another if one fails. These cluster servers are aware of each other’s status, often sending updates back and forth to ensure all systems and components are online.
Failover is a method of operational backup where the functions of one component are taken up by a backup component in the event of a failure or unexpected downtime. If a disruption occurs, tasks are seamlessly offloaded automatically to a standby system so the process continues without interruption for users.
Cloud-based environments offer highly reliable failback capabilities. The system handles workload transfers and backup restoration faster than traditional disaster recovery methods. After solving problems at the primary server, the application and workloads can be transferred back to the original location or primary system.
Other recovery techniques typically take longer as the migration uses physical servers deployed in a separate location. Depending on the volume of data you are backing up, you might consider migrating your data in a phased approach. While backup and failover processes are often automated in cloud-based systems, you still want to regularly test the operation on specific servers and zones to ensure data is not impacted or corrupted. Do you want to learn more about cloud migrations? Then check out our blog showing the top five questions to ask before migrating your data.
You can also download those questions here!
Redundancy ensures you can recover critical information at any given time, regardless of the type of event or how the data was lost. You can achieve this through a combination of hardware and software. The goal is to ensure continuous operation in the event of a failure or catastrophic event.
If a main server or system fails for any reason, the secondary systems are already online and take over seamlessly. Examples of redundant components include multiple cooling or power modules within a server or a secondary network switch, ready to take over if the primary switch falters. A cloud environment can provide a level of redundancy that would be very expensive to create using an on-site server farm or other system.
The environment achieves this level of redundancy with additional hardware and by having the data center infrastructure equipped with multiple fail-safe and backup measures. By making use of specialized services and economies of scale, cloud solutions can provide much simpler and more cost-efficient backup capabilities than other options.
Backup and Recovery:
Thanks to its virtualization capabilities, cloud computing takes a completely different approach to disaster recovery. This approach encapsulates infrastructure into a single software or virtual server bundle. When a disaster occurs, the system duplicates the virtual server to a separate data center and loads it onto a virtual host. This can substantially decrease recovery time compared to traditional (physical hardware) methods. For many businesses, cloud-based disaster recovery offers the only viable solution for ensuring business continuity and long-term survival.
Keeping a Cloud Architecture Safe
Security, of course, is a major concern when it comes to the cloud and the data stored in it. You have an obligation to protect any data your store in the cloud. This includes both protecting it from outside sources and from internal users who should not have access to it.
To safeguard your cloud architecture, you will need to deploy a number of different best practices.
You should assign the appropriate role to all users on the system. You will need to define each role and give it access to only the applications and data needed to fulfill that role. When an employee leaves or no longer needs access, that access should be revoked immediately.
Deploying two-factor authentication across the infrastructure will help prevent attacks from outside factors. This method helps reduce unauthorized logins as well as identify compromised accounts.
The system should delete data that is no longer needed promptly. It should also be permanently removed. You need to ensure that this is done across all backup databases as well as the active database to prevent any trace of this data from remaining and being re-introduced.
Your cloud architecture may be routinely under attack by various threats, but if you have no monitoring software in place, you may never know it. These automated tools constantly scan the system for irregular access, viruses, and compromised accounts. You will be able to take a more proactive stance against these threats by monitoring for them.
Regularly Test for Weaknesses
Creating a defensive system for your cloud architecture is not a one-time process. You need to regularly test those defenses for weaknesses using penetration tests. These tests need to take into account the most recent attacks that have been launched against cloud architecture. By performing regular testing, you can discover gaps in your security and address them before they are used against you.
Are These Architecture Worth the Money?
Is it worth spending the upfront cost associated with building a high availability cloud architecture? It depends on your overall goals, but in many cases, absolutely.
If you need a system with 99.99% or better uptime, then the high redundancy and availability that this type of cloud architecture provides is a requirement. The seamless transition to backup servers, databases, and zones cannot be achieved otherwise. However, if you are simply looking for a disaster recovery or backup system, another option may meet those needs without the cost. No matter what type of cloud architecture you need, BACS IT is here to help.