Azure Storage ensures data durability and availability by storing multiple copies of data. By default, data is replicated three times within the primary region. Organizations can choose from different redundancy models to balance cost with availability and resilience requirements.
Overview
All redundancy options provide multiple copies of data. The choice of replication strategy involves a trade‑off between cost, durability, and protection against different types of failures.
Locally Redundant Storage (LRS)
- Replicates data three times within a single datacenter in the primary region.
- Durability: at least 11 nines (99.999999999%) over a year.
- Most cost‑effective redundancy option.
- Protects against server rack and drive failures but not against datacenter‑level disasters.
Zone‑Redundant Storage (ZRS)
- Replicates data across three separate availability zones within the same region.
- Durability: at least 12 nines (99.9999999999%) over a year.
- Protects against datacenter‑level disasters such as flooding or fire within a single zone.
Geo‑Redundant Storage (GRS)
- Synchronously replicates data three times within a single location using LRS.
- Asynchronously replicates the data to a secondary region (Azure regional pair), also using LRS.
- Durability: at least 16 nines (99.99999999999999%) over a year.
- Provides protection against regional outages but introduces potential lag due to asynchronous replication.
Geo‑Zone‑Redundant Storage (GZRS)
- Combines ZRS and GRS for maximum durability and resilience.
- Data is synchronously replicated across availability zones in the primary region, then asynchronously replicated to a secondary region.
- Provides both zone‑level and regional disaster recovery.
Conclusion
Azure Storage redundancy options allow organizations to select the appropriate balance of cost, durability, and disaster recovery capabilities. LRS offers the lowest cost for localized resilience, while ZRS, GRS, and GZRS provide increasing levels of protection against datacenter‑wide and regional failures.