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Microsoft has kicked off a public preview of its Read-Access Geo Redundant Storage (RA-GRS), a feature for the company’s growing Windows Azure cloud storage platform that improves access to data in the event of an outage.
Steven Martin, general manager for Windows Azure, explained in a blog post that “RA-GRS provides read access to your secondary storage replica should the storage account on the primary location become unavailable.” Localized events should have little impact on an organization’s ability to grab data from their Azure Storage accounts he suggested, since “the secondary location is hundreds of miles from the primary location, RA-GRS provides both data durability and improved data access.”
“As customers increasingly rely on the cloud for business critical solutions, the durability of data and ability to access data during a catastrophic event becomes paramount,” wrote Martin.
The replication-enhancing option provides Azure Storage accounts with an endpoint name for a secondary endpoint. Read requests can then be sent to the secondary endpoint and administrators can query the endpoint to determine an account’s replication lag time, noted Martin.
“Since replication to the secondary region is done asynchronously, this provides an eventual consistent version of the data to read from,” informed Windows Azure Storage staffers Jai Haridas and Brad Calder in a separate Windows Azure Storage Team Blog post that offers an extended technical walk-through. The ‘opt-in’ feature requires that an Azure Storage account be geo-replicated, they added.
The feature builds on Windows Azure Storage’s Geo Redundant Storage (GRS) option. “A geo redundant storage account has its blob, table and queue data replicated to a secondary region hundreds of miles away from the primary region,” explained Haridas and Calder.
An accompanying chart spells out current primary and secondary location pairings for storage accounts. For example, Microsoft’s North Central U.S. cloud data center is paired with its South Central U.S. facility, and vice-versa. A northern European site is paired with one in western Europe, while East Asia and Southeast Asia share a similar link. (RA-GRS is currently not available in North China and East China).
RA-GRS “provides a higher read availability (99.99+ percent) for a storage account over GRS (99.9+ percent),” said Haridas and Calder. Write availability stays the same as GRS, currently at 99.9 percent.
“In terms of pricing, the capacity (GB) charge is slightly higher for RA-GRS than GRS, whereas the transaction and bandwidth charges are the same for GRS and RA-GRS,” they added. Until Feb. 2014, Microsoft is charging the same for RA-GRS as GRS, $0.095 per GB for the first TB per month, dropping down to $0.055, and below, as the TBs pile up.
Come February, the company plans to charge $0.105 per GB for the first TB per month. When RA-GRS eventually enters general availability, it will cost $0.12 per GB for the first TB per month, according to Microsoft’s pricing chart.