How to build resilient IT infrastructure?

Resilient IT infrastructure refers to the ability of an organisation’s information technology (IT) systems and infrastructure to withstand and recover from disruptive events, such as natural disasters, power outages, cyber-attacks, and other emergencies. A resilient IT infrastructure is designed to provide continuous availability and accessibility of critical data and services, even in the face of significant disruptions.

This can be achieved through a combination of strategies such as:

Disaster Recovery Planning: Having a well-defined disaster recovery plan in place to quickly restore critical systems and data in the event of a disruption.
High Availability: Implementing high-availability solutions, such as redundant servers and storage systems, to ensure that critical systems are always available and accessible.
Data Backup and Replication: Regularly backing up and replicating critical data to ensure that it is protected and can be recovered in the event of a disaster.
Cybersecurity: Implementing strong cybersecurity measures to protect against cyber-attacks and prevent data loss or theft.
Network and System Monitoring: Continuously monitoring the IT infrastructure to detect and respond to disruptions and failures in real-time.

Having a resilient IT infrastructure is critical for organisations to minimize the impact of disruptive events and ensure the continuity of their operations and services.

What is the difference between Disaster Recovery and High Availability?

Disaster Recovery (DR) and High Availability (HA) are related but distinct concepts in the field of information technology.

High Availability refers to the ability of a system to remain operational and accessible to users during normal operations, with minimal downtime or disruptions. The goal of High Availability is to ensure that systems are always available to meet the needs of the business.

Disaster Recovery, on the other hand, refers to the processes, policies, and procedures that are put in place to ensure that systems can be recovered and restored to normal operations following a disaster, such as a natural disaster, a cyber attack, or a hardware failure. The goal of Disaster Recovery is to minimize the impact of a disaster on business operations and to ensure that systems can be restored to normal operations as quickly as possible.

In summary, High Availability focuses on ensuring that systems are always available, while Disaster Recovery focuses on ensuring that systems can be recovered following a disaster. Both concepts are important to ensuring the reliability and resilience of IT systems, and they are often used together as part of a comprehensive IT resilience strategy.

What are the core concepts of Disaster Recovery?

Disaster Recovery (DR) is a set of processes, policies, and procedures that are put in place to ensure that systems can be recovered and restored to normal operations following a disaster. The following are the core concepts of Disaster Recovery:

Risk assessment: A thorough evaluation of the risks and potential impacts associated with different types of disasters.
Business impact analysis: An analysis of the impact that a disaster would have on business operations, including the costs and risks associated with data loss and downtime.
Recovery strategy: A plan that outlines the steps required to recover systems and restore normal business operations following a disaster.
Backup and data replication: The creation of regular backups and the replication of data to ensure that data is protected and that systems can be restored quickly in the event of a disaster.
Testing and validation: Regular testing and validation of disaster recovery plans to ensure that they are effective and that systems can be recovered quickly in the event of a disaster.
Communication and coordination: Effective communication and coordination among IT teams, business stakeholders, and other key personnel to ensure that disaster recovery plans are effectively executed in the event of a disaster.
Continuous improvement: Regular review and refinement of disaster recovery plans and processes to ensure that they remain effective and relevant as business operations change.
Recovery Point Objective (RPO) and Recovery Time Objective (RTO): Critical factors that play a key role in Disaster Recovery (DR) planning and implementation.

These core concepts of Disaster Recovery form the foundation of an effective DR strategy, helping organisations to minimize the impact of disasters and to ensure that systems can be restored to normal operations as quickly as possible.

How to design an effective DR strategy?

Here’s a general outline of how you can design an effective DR strategy:

Define your goals and requirements: Determine what your organization needs to recover in the event of a disaster, and set goals and objectives for your DR strategy. Consider factors such as recovery time objectives (RTOs) and recovery point objectives (RPOs), which define the maximum acceptable amount of time and data loss during a recovery.
Assess your risks: Identify potential threats to your IT systems and data, and evaluate their likelihood and potential impact. Consider both external threats, such as natural disasters and cyberattacks, as well as internal threats, such as hardware failures or human error.
Choose a DR strategy: Based on your goals and risk assessment, decide on the best DR strategy for your organization. Options include cold, warm, and hot site recovery, as well as hybrid approaches that combine elements of each. Consider factors such as cost, complexity, and the need for ongoing testing and maintenance.
Create a DR plan: Develop a detailed DR plan that outlines the steps you’ll take to recover your systems and data in the event of a disaster. This plan should include procedures for testing, data backup and restoration, and communication with stakeholders.
Implement and test your DR strategy: Put your DR plan into action, and conduct regular testing to ensure that it works as expected. Consider conducting annual tabletop exercises or live drills to simulate a disaster scenario and assess the readiness of your DR plan.
Continuously monitor and update: Regularly review and update your DR plan to ensure that it remains relevant and effective. Stay informed about new technologies and best practices, and incorporate changes as needed to keep your DR strategy up to date.

This is a general outline, and the specifics of your DR strategy will depend on the size, complexity, and criticality of your IT systems and applications. Working with a knowledgeable vendor or consultant can help ensure that your DR strategy is well-designed, implemented, and tested to meet the needs of your organization.

What types of DR strategies could I use?

There are several types of Disaster Recovery (DR) strategies that organizations can choose from, each with its own advantages and disadvantages. Here are some of the most common DR strategies:

Cold Site Recovery: A cold site is a pre-configured IT infrastructure that is ready to be activated in the event of a disaster. This type of DR strategy is typically the most affordable option, as it only requires a minimal investment in hardware and infrastructure. However, it also has the longest recovery time, as all systems and applications must be installed and configured from scratch after a disaster.
Warm Site Recovery: A warm site is a partially configured IT infrastructure that includes some systems and applications that are already in place and can be quickly activated in the event of a disaster. This type of DR strategy provides a faster recovery time than a cold site, but is more expensive and requires a higher level of investment in hardware and infrastructure.
Hot Site Recovery: A hot site is a fully configured IT infrastructure that is designed to be activated immediately in the event of a disaster. This type of DR strategy provides the fastest recovery time and is the most expensive option, as it requires a significant investment in hardware and infrastructure, as well as ongoing maintenance and testing.
Virtual Site Recovery: Virtual site recovery is a DR strategy that uses virtualization technology to create and manage virtualized IT systems and applications that can be quickly activated in the event of a disaster. This type of DR strategy provides a fast recovery time and can be less expensive than a hot site, but requires a high level of expertise in virtualization technology.
Remote Replication: Remote replication is a DR strategy that involves replicating data and applications to a remote location in real-time, so that they can be quickly activated in the event of a disaster. This type of DR strategy can provide a fast recovery time and is typically less expensive than a hot or warm site, but requires a reliable network connection and careful management of data to ensure consistency and accuracy.
Hybrid DR: Hybrid DR is a combination of two or more DR strategies, such as using a hot site for critical applications and a warm site for less critical systems. This type of DR strategy provides a flexible and customizable approach that can be tailored to meet the specific needs and budgets of an organization.

The right DR strategy for your organization will depend on factors such as the size, complexity, and criticality of your IT systems and applications, as well as your recovery time and data loss objectives. It’s important to carefully evaluate your options and choose a DR strategy that provides the right balance of cost, complexity, and reliability to meet your needs.

How do I design for High Availability?

Designing for high availability (HA) is a critical aspect of building a resilient IT infrastructure. Here are some best practices for designing a high availability IT infrastructure:

Redundant components: Implement redundant components, such as servers, storage systems, network switches, and power supplies, to ensure that critical systems are always available and accessible.
Load balancing: Implement load balancing solutions to distribute workloads evenly across multiple servers, reducing the risk of any single server becoming a single point of failure.
Cluster and failover solutions: Implement cluster and failover solutions to automatically switch to a redundant component in the event of a failure, minimizing downtime.
Network redundancy: Implement redundant network connections and network switches to ensure that network traffic can be redirected in the event of a failure.
Data replication: Implement data replication solutions to ensure that critical data is constantly backed up and available in multiple locations, reducing the risk of data loss in the event of a disaster.
Automated monitoring and response: Implement automated monitoring and response solutions to detect and respond to disruptions and failures in real-time, minimizing downtime.
Regular testing: Regularly test the high availability infrastructure to ensure that it is functioning correctly and that the recovery process is working as intended.

By following these best practices, you can design a highly available IT infrastructure that minimizes downtime and ensures the continuous availability and accessibility of critical systems and data.

Do stateless applications help in High Availability?

Yes, stateless applications can help in achieving High Availability (HA). Stateless applications do not maintain any state or session data on the server, which means that they can easily be scaled horizontally by adding more instances or nodes. This allows for more efficient load balancing and the ability to redirect traffic to a different instance in the event of a failure, which helps to ensure high availability.

Additionally, stateless applications can be deployed across multiple availability zones, data centers, or cloud regions, which can help to ensure that the application remains available even in the event of a regional disaster or outage.

Overall, stateless applications provide greater flexibility and resilience in the face of failures, making them well-suited for HA environments. However, it’s worth noting that not all applications can be made stateless, and in some cases, maintaining state may be necessary for the correct functioning of the application.

Stateless vs Stateful applications

Stateless and stateful are terms used to describe the architecture of applications and their handling of user data.

Stateless applications do not store any information or data about a user’s session on the server. This means that each request made to the application is treated as a new request, with no context or knowledge of previous requests. Because stateless applications don’t maintain state on the server, they can be easily scaled and replicated, and they are less likely to experience issues with session persistence.

Stateful applications, on the other hand, store information about a user’s session on the server. This information can include the user’s session ID, shopping cart contents, or other data related to the user’s session. Because stateful applications maintain state on the server, they are more complex and difficult to scale, but they offer greater persistence and continuity of user experience.

In general, stateless applications are preferred for their scalability and ease of management, while stateful applications are preferred for their persistence and continuity of user experience. The choice between stateless and stateful architecture depends on the specific requirements of the application and the needs of the business.

How do I implement HA in the cloud?

Implementing High Availability (HA) in the cloud involves using cloud technologies and best practices to ensure that your applications and services remain available and accessible, even in the event of a failure. Here are some steps you can take to implement HA in the cloud:

Design for failure: When designing your cloud infrastructure, assume that failures will occur and design your systems to be resilient to those failures.
Use auto-scaling: Use auto-scaling to dynamically add or remove compute resources as needed, which can help ensure that your applications remain available and responsive, even during periods of high traffic.
Use load balancing: Use load balancing to distribute incoming traffic across multiple instances of your applications, which can help ensure that your applications remain available and responsive, even during periods of high traffic.
Use multi-availability zones: When possible, deploy your cloud resources across multiple availability zones within a cloud region to ensure that your applications and services remain available even in the event of a failure in one availability zone.
Use managed services: When possible, use managed services, such as managed databases and managed storage services, to reduce the operational overhead associated with managing your cloud infrastructure.
Use backups and disaster recovery: Regularly back up your data and implement disaster recovery strategies to ensure that your data is protected and that you can recover quickly in the event of a failure.
Monitor and test: Regularly monitor your cloud infrastructure and test your disaster recovery strategies to ensure that they are effective and that your systems remain available and accessible, even in the event of a failure.

By following these steps, you can help ensure that your applications and services remain available and accessible, even in the event of a failure, when implementing HA in the cloud.

What types of HA strategies can I use?

Here are some of the most common HA strategies:

Active/Active: An active/active HA strategy involves multiple instances of a system or application running simultaneously, with each instance actively processing requests. In the event of a failure, the remaining instances take over processing requests, ensuring that the system remains available to users.
Active/Passive: An active/passive HA strategy involves a primary instance of a system or application that is actively processing requests, with a secondary instance standing by in a passive mode. In the event of a failure, the secondary instance takes over processing requests, ensuring that the system remains available to users.
N+1: An N+1 HA strategy involves deploying multiple instances of a system or application, with one instance designated as the primary and the others as backups. In the event of a failure, one of the backups takes over as the primary, ensuring that the system remains available to users.
Load Balancing: Load balancing is a HA strategy that involves distributing incoming requests evenly across multiple instances of a system or application. In the event of a failure, the load balancer automatically redirects requests to the remaining instances, ensuring that the system remains available to users.
Clustering: Clustering is a HA strategy that involves grouping multiple instances of a system or application together, with each instance able to take over processing requests in the event of a failure. Clustering can provide a high level of availability and reliability, but can be complex and expensive to implement and maintain.
Virtualization: Virtualization is a HA strategy that involves running multiple instances of a system or application on a shared set of physical resources, with each instance isolated from the others in a virtual environment. Virtualization can provide a high level of availability and reliability, and can be less expensive than other HA strategies, but can also increase the complexity of managing and maintaining the systems.

The right HA strategy for your organization will depend on factors such as the size, complexity, and criticality of your IT systems and applications, as well as your availability and performance requirements. It’s important to carefully evaluate your options and choose an HA strategy that provides the right balance of cost, complexity, and reliability to meet your needs.

What is RTO and RPO?

RTO (Recovery Time Objective) and RPO (Recovery Point Objective) are two important concepts in disaster recovery and business continuity planning.

Recovery Time Objective (RTO): RTO is the maximum amount of time that an organisation can afford to be without its IT systems and applications following a disruption. The RTO represents the target time for restoring normal business operations after a disaster.

Recovery Point Objective (RPO): RPO is the maximum amount of data that an organisation can afford to lose following a disruption. It represents the point in time to which an organisation must recover its data in order to minimize the impact of the disaster.

For example, an organization with a critical system may have an RTO of 4 hours and an RPO of 1 hour, meaning that they need to be able to restore normal operations within 4 hours of a disaster and must recover all data up to 1 hour before the disaster occurred.

RTO and RPO are critical considerations in disaster recovery planning, as they help organisations determine the level of investment required in their disaster recovery solutions and the resources needed to support those solutions. They are also important metrics for evaluating the effectiveness of a disaster recovery plan.

How do I calculate RTO?

Calculating Recovery Time Objective (RTO) involves determining the amount of time required to recover from a disruptive event and restore normal business operations. Here are the steps for calculating RTO:

Identify critical systems and applications: Determine which systems and applications are critical to your business operations and need to be recovered in the event of a disaster.
Determine the impact of a disruption: Evaluate the impact that a disruption would have on your business operations, including the costs and risks associated with downtime.
Establish an RTO target: Based on the impact of a disruption, establish a target RTO that represents the maximum amount of time that your business can afford to be without its critical systems and applications.
Identify dependencies: Identify any dependencies between critical systems and applications, such as data dependencies or interdependencies between systems.
Establish recovery time estimates: Based on the dependencies identified, estimate the time required to recover each critical system and application.
Determine the total RTO: Sum the recovery time estimates for each critical system and application to determine the total RTO for your business.
Review and refine: Regularly review and refine your RTO calculations to ensure that they remain accurate and relevant as your business operations change.

By following these steps, you can calculate a realistic RTO that reflects the time required to restore normal business operations after a disruptive event. This information can be used to inform your disaster recovery planning and to help ensure that you have the resources and solutions in place to meet your RTO target.

How do I calculate RPO?

Calculating Recovery Point Objective (RPO) involves determining the maximum amount of data that can be lost following a disruptive event. Here are the steps for calculating RPO:

Identify critical data: Determine which data is critical to your business operations and needs to be recovered in the event of a disaster.
Determine the impact of data loss: Evaluate the impact that data loss would have on your business operations, including the costs and risks associated with data loss.
Establish an RPO target: Based on the impact of data loss, establish a target RPO that represents the maximum amount of data that your business can afford to lose.
Identify data sources: Identify all sources of critical data, such as databases, file servers, and cloud storage systems.
Establish data replication intervals: Based on the data sources identified, determine the frequency with which data is replicated and stored in a separate location.
Determine the RPO: Based on the data replication intervals, determine the RPO by calculating the amount of time between data replications.
Review and refine: Regularly review and refine your RPO calculations to ensure that they remain accurate and relevant as your business operations change.

By following these steps, you can calculate a realistic RPO that reflects the maximum amount of data that can be lost following a disruptive event. This information can be used to inform your disaster recovery planning and to help ensure that you have the resources and solutions in place to meet your RPO target.

Examples of the most common challenges?

Implementing and maintaining a High Availability (HA) or Disaster Recovery (DR) strategy can present a number of challenges, including:

Cost: Implementing and maintaining an HA or DR strategy can be expensive, requiring significant investment in hardware, software, and staffing resources.
Complexity: HA and DR strategies can be complex to implement and maintain, requiring a high level of technical expertise and careful planning to ensure that the systems and processes are properly configured and tested.
Scalability: As an organization grows and evolves, its HA and DR requirements may change, requiring updates to the systems and processes to ensure that they can scale to meet changing needs.
Testing: Regular testing of HA and DR systems and processes is critical to ensuring that they will work as intended in the event of a failure or disaster. However, testing can be time-consuming and disruptive to normal operations, and may require significant resources and planning.
Integration: Integrating HA and DR systems and processes with existing IT systems and applications can be challenging, requiring careful coordination and planning to ensure that the systems and data are properly synchronized and protected.
Data Management: Managing data in a manner that ensures consistency and accuracy is a critical component of any HA or DR strategy. This can be challenging, especially when dealing with large amounts of data or complex data relationships.
Network Connectivity: Reliable network connectivity is essential for many HA and DR strategies, especially those that involve remote replication or virtual site recovery. However, network connectivity can be disrupted by a variety of factors, including outages, latency, and security breaches, which can impact the effectiveness of the HA or DR strategy.

These challenges underscore the importance of careful planning, testing, and continuous improvement in the design and implementation of an HA or DR strategy. By anticipating and addressing these challenges, organizations can ensure that their systems and data are protected and available, even in the event of a failure or disaster.

Sample DR runbook (per critical application)

A runbook is a documented set of procedures and steps that are followed to perform a specific task or process. In the context of Disaster Recovery (DR), a runbook provides a step-by-step guide for responding to a disaster and recovering critical systems and data. Here is a sample DR runbook that can serve as a template for building your own runbook:

Introduction: Provide an overview of the purpose and scope of the DR runbook, including a description of the critical systems and data that are protected by the DR plan.
Disaster Declaration: Define the criteria for declaring a disaster, including the types of events that would trigger a declaration, and the responsibilities of the individuals who will be responsible for declaring a disaster.
Emergency Response: Describe the immediate actions that must be taken in response to a disaster, including shutting down critical systems, securing data and equipment, and activating the DR plan.
Activation of DR Site: Describe the steps involved in activating DR, including establishing communications, verifying system and data availability, and initiating data replication or backup processes.
Data Restoration: Detail the steps involved in restoring critical data, including data backup and recovery processes, data validation and reconciliation, and testing of restored systems and data.
System Recovery: Outline the steps involved in recovering critical systems, including installation and configuration of hardware and software, data replication and synchronization, and testing of recovered systems to ensure that they are functioning as intended.
Communication and Coordination: Describe the communication and coordination processes that will be used to keep stakeholders informed during the DR process, including the use of status updates, conference calls, and other methods of communication.
Post-Disaster Review: Outline the steps involved in reviewing and evaluating the DR process after a disaster, including a review of the DR plan, identification of areas for improvement, and recommendations for updating the DR plan.
Appendices: Include any additional information or materials that are relevant to the DR plan, including maps, contact lists, configuration documentation, and other supporting materials.

This sample DR runbook provides a basic outline for building a DR plan, and can be customized to meet the specific needs and requirements of your organization. By following these steps, you can help ensure that your organization is prepared to respond to a disaster and recover critical systems and data as quickly and effectively as possible.

Sample HA runbook (per critical application)

Sample HA runbook

A runbook is a documented set of procedures and steps that are followed to perform a specific task or process. In the context of High Availability (HA), a runbook provides a step-by-step guide for responding to a failure or disruption of critical systems and ensuring that they remain available to users. Here is a sample HA runbook that can serve as a template for building your own runbook:

Introduction: Provide an overview of the purpose and scope of the HA runbook, including a description of the critical systems that are protected by the HA plan.
Failure Declaration: Define the criteria for declaring a failure, including the types of events that would trigger a declaration, and the responsibilities of the individuals who will be responsible for declaring a failure.
Emergency Response: Describe the immediate actions that must be taken in response to a failure, including identifying the root cause of the failure, initiating failover procedures, and activating the HA plan.
Failover to Secondary System: Outline the steps involved in failing over to a secondary system, including activating the secondary system, synchronizing data, and redirecting user traffic to the secondary system.
Monitoring and Verification: Detail the steps involved in monitoring and verifying the availability of the secondary system, including regular health checks, performance monitoring, and testing of failover procedures.
Communication and Coordination: Describe the communication and coordination processes that will be used to keep stakeholders informed during the HA process, including the use of status updates, conference calls, and other methods of communication.
Restoration of Primary System: Outline the steps involved in restoring the primary system, including verifying system and data availability, testing of the primary system, and re-establishing the primary system as the active system.
Post-Failure Review: Outline the steps involved in reviewing and evaluating the HA process after a failure, including a review of the HA plan, identification of areas for improvement, and recommendations for updating the HA plan.
Appendices: Include any additional information or materials that are relevant to the HA plan, including maps, contact lists, configuration documentation, and other supporting materials.

This sample HA runbook provides a basic outline for building a HA plan, and can be customized to meet the specific needs and requirements of your organization. By following these steps, you can help ensure that your organization is prepared to respond to a failure or disruption of critical systems and maintain availability for users.