System requirements

For the scope of our problem, we will only consider the following resources in our architecture,

• Virtual machines
• Web servers
• Databases
• Virtual networks
• Traffic Manager
• Load balancer
• Analytics database.

Functional:

1. Data Backup:
2. The system should automatically back up virtual machines, web servers, databases, virtual networks, and analytics databases on a regular basis.
3. It should support various backup types such as full backups, incremental backups, and differential backups.
4. It should ensure that backups are stored securely and offsite to prevent data loss in case of on-premises disasters.
5. System Replication:
6. The system should replicate virtual machines, web servers, and databases in real-time or near-real-time to ensure redundancy.
7. It should utilize synchronous or asynchronous replication depending on the recovery objectives and latency tolerance.
8. It should replicate data across geographically diverse locations to mitigate regional disasters.
9. Failover Procedures:
10. The system should accept failover rules and procedures to automatically switch traffic from primary systems to redundant systems in case of a disaster.
11. It should ensure failover is seamless and transparent to end-users to minimize downtime.
12. Risk Assessment:
13. The user should conduct regular risk assessments to identify potential threats and vulnerabilities to the IT systems.
14. User should assess the impact of each risk on critical assets and prioritize them accordingly.
15. Identify Critical Assets:
16. The system should identify critical virtual machines, web servers, databases, and analytics databases that are essential for business operations.
17. It should classify assets based on their importance and criticality to prioritize recovery efforts.
18. Define Recovery Objectives:
19. It should define recovery time objectives (RTOs) and recovery point objectives (RPOs) for each critical asset.
20. It should ensure RTOs and RPOs align with business requirements and acceptable levels of downtime and data loss.

Non-Functional:

1. Performance:
2. Ensure minimal impact on system performance during data backup, replication, and failover operations.
3. Define performance metrics and thresholds to monitor system performance and ensure it meets acceptable levels.
4. Scalability:
5. Design the disaster recovery system to scale seamlessly as the organization grows and as data volumes increase.
6. Ensure scalability across virtual machines, web servers, databases, and other components to accommodate future growth.
7. Reliability:
8. Ensure high reliability of the disaster recovery system to minimize the risk of failures or downtime.
9. Implement redundancy and fault-tolerant mechanisms to ensure system availability even in the event of component failures.
10. Security:
11. Implement robust security measures to protect data during backup, replication, and failover processes.
12. Ensure data encryption, access controls, and secure transmission protocols are in place to prevent unauthorized access or data breaches.
13. Compliance:
14. Ensure compliance with relevant regulations and industry standards for data protection and disaster recovery.
15. Regularly audit the disaster recovery system to ensure compliance with regulatory requirements.

Capacity estimation

For capacity estimation we need to consider that our internal components like Database Backup Component, VM-Disk Backup Component should be able to take backups and snapshots efficiently even when the number of database copies and vm-disks increase in number.

let us consider a system where we have 100 Virtual machines, 2 VM disks, that is 200 VM-disks total, 100 database servers in each region. So our systems should be able to handle replication and do backup for the above systems within reasonable times.

Replication

• For Virtual machines and databases which are classified under High Change Rate Environment, we will need to have a Continuous Data Protection (CDP) with Near-Real-Time Replication (e.g., Every 15 Minutes)
• For Moderate Change Rate Environment : Replication Frequency is every few hours (e.g., 4-6 Hours)
• Low Change Rate Environments replication frequency is Daily to Weekly

Backup

• For Virtual machines and databases which are classified under High Change Rate Environment, we will need to have a backup hourly to every few hours
• For Moderate Change Rate Environment : Backup Frequency is Daily
• Low Change Rate Environments replication frequency is Daily or Weekly

Backup Retention

• Critical Systems with Stringent RPO and RTO Requirements:
• Continuous Data Protection (CDP): Retain backups for 30 days to 1 year.
• Retention Period for Full Backups: 7 to 30 days.
• Retention Period for Incremental or Differential Backups: 24 to 72 hours.
• Non-Critical Systems or Historical Data:
• Weekly or Monthly Backups: Retain backups for 1 to 5 years.
• Retention Period for Full Backups: 30 days to 5 years.
• Retention Period for Incremental or Differential Backups: 7 to 30 days.

API design

Below are a few API's we would need for our system, these are not exhaustive lists but some of the most essential ones.

Backup API's

1. Create Full Backup API:
2. Description: This API allows the system to initiate the creation of a full backup for specified resources such as virtual machines, databases, or entire systems. It triggers the backup process to capture the current state of the resource and save it as a complete backup image.
3. Get List of Backups API:
4. Description: This API retrieves a list of available backups for a given resource or set of resources. It provides metadata and information about each backup, such as timestamps, versions, and sizes, enabling administrators to manage and select backups for recovery purposes.
5. Apply Backup Image API:
6. Description: This API facilitates the restoration of resources from a backup image. It allows the system to apply a selected backup image to the corresponding resource, restoring it to a previous state. This process may involve restoring virtual machines, databases, or other components from the backup data.

Replication API's

1. Start Replication API:
2. Description: This API initiates the replication process for specified resources, such as virtual machines or databases. It triggers the creation of replicated copies of the resources to ensure redundancy and availability.
3. Pause Replication API:
4. Description: This API temporarily halts the replication process for specified resources. It allows administrators to pause replication operations for maintenance tasks or to address performance issues without disrupting ongoing replication.
5. Resume Replication API:
6. Description: This API resumes the replication process for resources that were previously paused. It reactivates replication operations, allowing data to continue syncing between primary and secondary locations.
7. Get Replication Status API:
8. Description: This API retrieves the current status of replication for specified resources. It provides information about replication progress, replication lag, and any errors or issues encountered during the replication process.
9. Configure Replication Settings API:
10. Description: This API allows administrators to configure replication settings for specified resources. It includes parameters such as replication frequency, replication method (e.g., synchronous or asynchronous), and target replication location.
11. Failover Trigger API:
12. Description: This API initiates the failover process for resources in the event of a disaster or planned maintenance. It triggers the switchover from primary to secondary resources to ensure continuous availability and data access.
13. Failback Trigger API:
14. Description: This API initiates the failback process after a failover event. It facilitates the return of operations to the primary resources once they are restored and operational again, ensuring a seamless transition back to normal operations.

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

High-level design

Below are the components which will be require to support the disaster recovery system.

1. Database Backup Component:
2. Responsible for backing up databases regularly to ensure data protection.
3. Utilizes database-native backup mechanisms or backup agents to capture database backups.
4. Coordinates backup schedules and policies based on RPO requirements.
5. VM-Disk Backup Component:
6. Handles the backup of VM disks, including operating system and application data.
7. Utilizes hypervisor-based snapshots or backup agents installed within VMs for disk-level backups.
8. Supports incremental backups and deduplication to minimize backup storage requirements.
9. Smart Load Balancer:
10. Distributes incoming traffic across multiple backend servers or instances to optimize performance.
11. Monitors server health and dynamically adjusts traffic routing based on predefined policies.
12. Integrates with health monitoring and alerting systems to detect and respond to server failures.
13. Traffic Router:
14. Routes incoming traffic to appropriate destinations based on predefined rules and policies.
15. Utilizes DNS-based load balancing and failover mechanisms for traffic redirection.
16. Supports global server load balancing (GSLB) for optimizing traffic distribution across multiple data centers or cloud regions.
17. Configuration Store Database:
18. Stores configuration data and settings for the disaster recovery system components.
19. Provides a centralized repository for managing configuration changes and updates.
20. Cold Storage Database:
21. Stores backup data in a secure and cost-effective manner for long-term retention.
22. Utilizes storage technologies optimized for infrequently accessed data, such as object storage or archival storage services.
23. Secure Vault:
24. Stores sensitive information such as secrets, certificates, and encryption keys used by the disaster recovery system.
25. Implements strong access controls and encryption to protect sensitive data from unauthorized access.
26. Monitoring Service and Database:
27. Monitors the health and performance of the disaster recovery system components.
28. Collects and analyzes metrics, logs, and events to detect anomalies and performance issues.
29. Stores monitoring data in a centralized database for analysis and reporting.
30. Alerting or Notification Database:
31. Stores alerting and notification configurations, rules, and policies.
32. Generates alerts and notifications based on predefined thresholds and conditions.
33. Integrates with external notification services to notify stakeholders of critical events and incidents.
34. Configuration Service:
35. Provides a centralized platform for managing configuration settings and parameters for all components of the disaster recovery system.
36. Allows administrators to define and update configuration settings for individual components or groups of components.
37. Supports versioning and change tracking to ensure accountability and auditability of configuration changes.

Request flows

Explain how the request flows from end to end in your high level design. Also you could draw a sequence diagram using the diagramming tool to enhance your explanation...

Detailed component design

Dig deeper into 2-3 components and explain in detail how they work. For example, how well does each component scale? Any relevant algorithm or data structure you like to use for a component? Also you could draw a diagram using the diagramming tool to enhance your design...

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?