"Locally Redundant Storage (LRS) Account" is a storage account for which data is replicated synchronously only within a Primary Region.
"Zone Redundant Storage (ZRS) Account" is a storage account for which data is replicated across multiple facilities. These facilities may be within the same geographical region or across two geographical regions.
"Geographically Redundant Storage (GRS) Account" is a storage account for which data is replicated synchronously within a Primary Region and then replicated asynchronously to a Secondary Region. You cannot directly read data from or write data to the Secondary Region associated with GRS Accounts.
"Read Access Geographically Redundant Storage (RA-GRS) Account" is a storage account for which data is replicated synchronously within a Primary Region and then replicated asynchronously to a Secondary Region. You can directly read data from, but cannot write data to, the Secondary Region associated with RA-GRS Accounts.
| Replication strategy | LRS | ZRS | GRS | RA-GRS |
| Data is replicated across multiple facilities. | No | Yes currently available only for block blobs | Yes | Yes |
| Data can be read from the secondary location as well as from the primary location. | No | No | No | Yes secondary endpoint is similar to the primary endpoint, but appends the suffix –secondary to the account name. For example, if your primary endpoint for the Blob service is myaccount.blob.core.windows.net, then your secondary endpoint is myaccount-secondary.blob.core.windows.net. The access keys for your storage account are the same for both the primary and secondary endpoints. |
| Number of copies of data maintained on separate nodes. | 3 replicas each reside in separate fault domains and upgrade domains | 3 | 6 replicated three times asynchronously, across separate fault domains and upgrade domains in secondary region | 6 |
Related terms:
"Primary Region" is a geographical region in which data within a storage account is located, as selected by you when creating the storage account. You may execute write requests only against data stored within the Primary Region associated with storage accounts.
"Secondary Region" is a geographical region in which data within a GRS or RA-GRS Account is replicated and stored, as assigned by Microsoft Azure based on the Primary Region associated with the storage account. You cannot specify the Secondary Region associated with storage accounts.
"Geo Replication Lag" for GRS and RA-GRS Accounts is the time it takes for data stored in the Primary Region of the storage account to replicate to the Secondary Region of the storage account. Because GRS and RA-GRS Accounts are replicated asynchronously to the Secondary Region, data written to the Primary Region of the storage account will not be immediately available in the Secondary Region. You can query the Geo Replication Lag for a storage account, but Microsoft does not provide any guarantees as to the length of any Geo Replication Lag under this SLA.
A fault domain (FD) is a group of nodes that represent a physical unit of failure and can be considered as nodes belonging to the same physical rack.
An upgrade domain (UD) is a group of nodes that are upgraded together during the process of a service upgrade (rollout).
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