Warm Standby
Definition
Backup system that's partially running and can take over quickly but not instantly. Like having a car engine that's warmed up but not fully running.
Use Cases
- Netflix: Maintain service availability during regional outages by failing over critical components to another AWS region. — Netflix has publicly discussed multi-region resilience practices on AWS, including running critical services in more than one region and using automated failover mechanisms (for example, traffic management and capacity scaling) to continue operating if a region becomes impaired. This aligns with a warm-standby approach when the secondary region runs at reduced capacity until needed. (Improved resilience to regional failures and reduced downtime risk for streaming and supporting services.)
- Etsy: Disaster recovery for an e-commerce marketplace to keep the site available if a primary environment fails. — Etsy has shared engineering practices around reliability and incident response, including maintaining disaster recovery capabilities and the ability to restore services quickly. A common warm-standby implementation for marketplaces is to keep a minimal application stack and replicated data ready in a secondary location, then scale out and redirect traffic during an incident. (Faster recovery during major incidents compared with rebuilding from backups alone, while avoiding the full cost of always-on active/active capacity.)
Provider Equivalents
- AWS: AWS Elastic Disaster Recovery (DRS)
- Azure: Azure Site Recovery
- GCP: Google Cloud Backup and DR (formerly Actifio)
- OCI: OCI Full Stack Disaster Recovery (FSDR)
Frequently Asked Questions
- What's the difference between warm standby and hot standby?
- Hot standby keeps a fully running, production-sized copy of your system ready to take traffic almost immediately (often seconds). Warm standby keeps a smaller or partially running environment that can take over quickly, but usually needs a scale-up step (often minutes) before it can handle full production load.
- When should I use warm standby?
- Use warm standby when you need a relatively low recovery time (minutes rather than hours) but want to reduce cost compared with hot standby. It’s a good fit for customer-facing apps (e-commerce, SaaS, APIs) where downtime is expensive, but running full duplicate capacity 24/7 is not justified.
- How much does warm standby cost?
- Cost depends on what you keep running in the standby environment. Typical cost drivers include: (1) standby compute (smaller instance sizes or fewer nodes), (2) storage for replicated data and snapshots, (3) continuous replication or data transfer charges between regions/sites, (4) managed DR orchestration fees (if using a DR service), and (5) periodic testing costs. Warm standby is usually cheaper than hot standby because standby capacity is reduced, but more expensive than cold standby because some resources run continuously.
Category: cloud
Difficulty: intermediate
Related Terms
See Also