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Azure Storage always stores multiple copies of your data so that it is protected from planned and unplanned events such as hardware failures, network or power outages which ensures that your storage meets the SLA.
When deciding which redundancy option is best for your scenario, consider the tradeoffs between lower costs and higher availability and durability. The factors that help determine which redundancy option you should choose include:
LRS – Locally Redundant.
- Your data is replicated synchronously, so that there are three copies within a single facility in a single region.
- Locally Redundant Storage (LRS) protects your data against server hardware failures but not against the failure of the facility itself.
ZRS – Zone Redundant.
- Your data is replicated synchronously, so that there are three copies across two or three facilities in a single region.
- Zone Redundant Storage (ZRS) is more redundant than LRS but does not protect against failures that affect a while region.
- ZRS is only available for BLOB storage.
GRS – Geo-Redundant.
- Your data is replicated asynchronously, with three copies of the data in the primary region using LRS, and three copies of the data stored in a secondary region.
- If there is failure at the primary region, Azure Storage will failover to the secondary region.
- Geo-Redundant Storage (GRS) is the most resilient of the replication schemes.
- GZRS supports block blobs, page blobs (except for VHD disks), files, tables, and queues.
RA-GZRS – Read-Access Geo-Zone-Redundant.
- Copies your data synchronously across three Azure availability zones in the primary region using ZRS.
- As with GRS, your data is replicated asynchronously across two regions.
- However, with read-access GRS, the three copies in the secondary region are enabled for read-only access to the data, if the primary region is unavailable.
- RA-GZRS supports block blobs, page blobs (except for VHD disks), files, tables, and queues.
Summary:
| LRS | ZRS | GRS | RA-GZRS | |
| How it works? | Multiple synchronous copies of data within single datacenter | Three copies of data across multiple datacenter within or across region. For Block BLOB only | Same as LRS plus multiple asynchronous copies to second datacenter miles away | Same as GRS plus read access the secondary datacenter |
| Total copies | 3 | 3 | 6 | 6 |
| Why Use it? | Economical local storage or data governance compliance | Economical, higher durability option for block BLOB storage | For protection against major datacenter outages or disasters | Provides read access to data during an outage for maximum data availability and durability |
| Availability SLA per year | 99.9% Read/Write | 99.9% Read/Write | 99.9% Read/Write | 99.9% Write 99.99% Read |
GZRS and RA-GZRS are supported in the following regions:
- Asia Southeast
- Europe North
- Europe West
- Japan East
- UK South
- US Central
- US East
- US East 2
- US West 2
For more details, visit MS Docs