Building a disaster recovery (DR) solution: Design considerations

Shishir Khandelwal
2 min readDec 15, 2024

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Design considerations

When designing a Disaster Recovery (DR) solution, several factors need to be considered to ensure that the system is resilient, cost-effective, and aligned with your organization’s recovery objectives. Here’s a comprehensive list:

1. Business Requirements

Recovery Time Objective (RTO):

  • How quickly should the system be restored after a disaster?
  • Example: 1 hour, 4 hours, or 24 hours.

Recovery Point Objective (RPO):

  • How much data loss is acceptable in the event of a disaster?
  • Example: 0 data loss (requires synchronous replication) vs. a few minutes (asynchronous replication).

Criticality of Workloads:

  • Identify mission-critical workloads versus those that can tolerate downtime.

2. Types of Failures to Mitigate

Application-Level Failures:

  • Ensure redundancy in application components like load balancers, application servers, and database connections.

Infrastructure-Level Failures:

  • Address issues like hardware failures, network outages, or storage issues.

Region-Level Failures:

  • Plan for scenarios like a full-region outage (e.g., AWS Mumbai region going offline).

Cloud Provider-Level Failures:

  • Rare but catastrophic, such as a cloud provider outage or breach. Consider multi-cloud setups.

3. DR Solution Architecture

Replication Strategy:

  • Synchronous vs. Asynchronous replication.
  • Multi-region, multi-zone, or multi-cloud setups.

Active-Active or Active-Passive Setup:

  • Active-Active: Both regions handle traffic simultaneously.
  • Active-Passive: One region handles traffic, while the other remains on standby.

Data Consistency Models:

  • Strong consistency, eventual consistency, or custom consistency requirements based on the workload.

4. Database-Specific Considerations

Replication Latency:

  • How quickly data is replicated across nodes or regions.
  • Example: MongoDB Atlas vs. Amazon RDS replication latency.

Quorum Configurations:

  • How many nodes must be available for the system to remain operational?

Pre-Warming:

  • For systems like MongoDB or RDS, how long does it take to prepare new nodes during failover?

5. Network Design

Latency:

  • Placement of nodes in geographically distributed regions.
  • Minimize latency while ensuring fault tolerance.

Bandwidth Costs:

  • Cross-region replication or communication costs.

6. Testing and Training

Strategy

  • How will you ensure your DR applications are ready to serve traffic all the time?

DR Playbook:

  • Document detailed steps for failover, recovery, and fallback.

Training:

  • Train teams to respond to DR scenarios effectively.

7. Cost and Resource Optimization

Budget Constraints:

  • Evaluate the costs of maintaining redundant resources (e.g., compute, storage, network).

Trade-offs:

  • The balance between high availability and cost.
  • Example: Use smaller instance types for passive nodes to reduce costs in an active-passive setup.

By addressing these seven considerations, you can design a robust DR solution that aligns with your operational, technical, and business needs.

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Shishir Khandelwal
Shishir Khandelwal

Written by Shishir Khandelwal

I spend my day learning AWS, Kubernetes & Cloud Native tools. Nights on LinkedIn & Medium. Work: Engineering @ PayPal.

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