Windows Azure New Service Alert: Read Access Geo Redundant Storage (RA-GRS)

Microsoft released the preview of its newest service, Read Access Geo Redundant Storage (RA-GRS), on December 12th. This service is designed to provide durability for business critical data.
This service creates a secondary replica with read-access of the desired storage account. Once enabled, it will also provide an endpoint name. In the event of a disaster, read requests can be routed directly to the secondary replica.

These are the key features of this service:
Follows eventual consistency
Uses the same Secret Keys & Shard Access Signatures as the primary storage account
To identify the secondary endpoint, the Secondary name is added to the endpoint name with a suffix “–secondary”.
Storage Analytics are also available
The Storage Client Library 3.0, REST v 2013-08-15, also supports RA-GRS in terms:
Querying the Last Sync Time
If the primary replica is not available, the secondary replica can be automatically retested

Keep these things in mind:
Any PUT/DELETE request made to this secondary replica will return an HTTP code 403.
Otherwise, the canonicalization of a resource to access the primary endpoint and the secondary endpoint must be the same. If it is not, it may not have the ability to read from the secondary side.

How does it work?
RA-GRS uses eventual asynchronous replica but because transactions across Partition Keys may occur out of order, the service uses a Recovery Point Objective Time called “Last Sync Time” to ensure data availability in the secondary replica. All updates to primary storage that occurred before the Last Sync Time will be available for reading from the secondary replica. Updates after the Last Sync Time might not be available.
The Last Sync Time values for Blobs, Queues, and Tables can be obtained by using the REST API “GetServiceStats”.

SLA: High Read Availability of 99.99+% (compared with normal GRS which is 99.9+%)

Pricing: Starting at $0.12/GB (preview: $0.0105/GB). Visit the pricing page for more information.

How do I use this service?
This service is currently available for a limited preview. Requests for this service must be made. After approval of the request, it can be enabled via the Windows Azure Management Portal by setting the replication property for the storage account to “Read Access Geo -Redundant Space”.
You can also enable it through the Windows Azure Service Management API by setting SecondaryReadEnabled value to true

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