Microsoft cloud storage mounts challenge with Windows Azure

Microsoft's cloud storage strategy relies on the Windows Azure service, while the Microsoft StorSimple gateway appliance helps with cloud integration.

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Amazon Web Services: Simple Storage Service, Glacier, AWS Storage Gateway

AT&T Synaptic Storage as a Service

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HP Cloud Object Storage

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Nirvanix Public Cloud Storage

Rackspace Hosting's Cloud Files

Microsoft claims its Windows Azure Storage cloud service stores more than 4 trillion objects and processes an average of 270,000 requests per second, peaking at 880,000. The service has been generally available since 2010.

Microsoft cloud storage performance was lauded recently when Nasuni Corp.'s testing found that Windows Azure Blob Storage finished first among six providers when compared on performance, availability and scalability.

Microsoft offers customers the choice of Local Redundant Storage (LRS), with three copies of data within a data center, and Geo Redundant Storage (GRS), with an additional three copies of data at a location at least 400 miles away.

In late 2012, Microsoft acquired StorSimple, which makes gateway appliances that run at a customer site and integrate with popular cloud-based storage options such as Azure and Amazon. That expanded Microsoft's cloud storage options and proved it was serious about gaining in this market.

Getting started/connected

Windows Azure is a development platform for building applications that make use of Microsoft's public cloud infrastructure, which includes disk-based storage at eight global locations. Windows Azure Storage is accessible through REST protocols over HTTP or HTTPS. Microsoft claims developers can build applications using any language, tool or framework, and that they can target Windows and Linux deployments. Companies that lack development skills or opt not to do the programming can connect to Windows Azure Storage through offerings from Microsoft partners. A new program called the Azure Storage Acceleration Program (ASAP) connects Windows Servers to Windows Azure Storage via a StorSimple appliance.

Developers who write applications for Windows Azure can choose from these four object abstractions:

  • Binary large objects (blobs) that provide a simple interface to store named files and their accompanying metadata; Azure service offers a choice of block blobs and page blobs.
  • Tables with a set of properties that provide scalable, structured storage.
  • Queues that have storage and message delivery for loosely coupled applications.
  • Drives that let an Azure application treat a page blob as a local drive with an NTFS file system; applications use existing NTFS APIs to access the network-attached drives.

The size limit for blobs and drives is 1 terabyte (TB). Tables can hold up to 255 properties; the combined size cannot exceed 1 megabyte (MB). There is no limit to the number of messages in a queue, but any message within a queue cannot exceed 8 kilobytes (KB).

To store data in Azure's Blob, Table and Queue services, users create a storage account in the geographic region where they want to store their data. The account can store up to 100 TB of blob, table and queue data. Customers can create up to five storage accounts through a Windows Azure subscription. According to Microsoft, customers can add more storage accounts by placing a support call to get the quota limit removed.

Data center locations

Customers can specify the geographic regions where their data will be stored. Sub-region service availability is viewable in the Windows Azure Service Dashboard. Microsoft may transfer data within a major geographic region (for example, within Europe) for data redundancy or other purposes. U.S. data centers are located in California, Illinois, Texas and Virginia; European data centers are in Ireland and the Netherlands; Asian data centers are in Hong Kong and Singapore.


Charges for Windows Azure Storage are based on storage utilization/capacity, the number of storage transactions and bandwidth usage for outbound data. Customers pay only for the Microsoft cloud storage resources they use. Microsoft offers a calculator to estimate costs.

Storage capacity: Microsoft bills for storage capacity based on the average daily amount of data stored (in GB) over a monthly period for Blob, Table, Queue and Windows Azure Drive storage. The default for storage accounts is geographically redundant. Customers turn off the default settings if they prefer locally redundant storage. For locally redundant storage, monthly pricing begins at $.070 per GB for the first TB, and rates decline on a graduated scale to $0.037 per GB for more than 5 PB to 9 PB. For geographically redundant storage, monthly pricing starts at $0.095 per GB for the first TB and rates slide in step increments to $0.055 for more than 5 PB to 9 PB. Customers need to contact Microsoft for capacities greater than 9 PB.

Transactions/Requests: Windows Azure charges 1 cent per 100,000 requests/transactions regardless of type.

For Windows Azure Drive storage, Microsoft bills only for the storage space used by the page blob and the read/write transactions to the page blob. Microsoft does not charge for read transactions that use the local drive cache. Microsoft bills for Windows Azure Drive use at the same rates as standard Windows Azure Storage.

Bandwidth/Data transfers (except Content Delivery Network): Inbound data sent to Windows Azure is free. The fee for outbound data is based on the total amount of data going out of the Windows Azure data centers via the Internet in a given billing cycle. No charges apply to data transfers between Microsoft Windows Azure services located within the same data center or sub-region. Normal rates apply to data transfers between sub-regions on both sides of the transfer.

Through June 30, Microsoft is running a promotion where the first 5 GB of outbound data transfers per billing month are free. Otherwise, outbound data transfers range from 12 cents per GB for the first 10 TB per month to 5 cents per GB for more than 150 TB to 500 TB per month for customers using Microsoft data centers in the U.S. and Europe. Higher rates apply for customers using Microsoft data centers in East and Southeast Asia. Customers need to contact Microsoft for outbound data transfers of more than 500 TB per month.

(Note: All pricing information is valid as of April 1, 2013)

Service-level agreement

Microsoft guarantees that at least 99.9% of the time it will successfully process correctly formatted requests to add, update, read and delete data. The company also guarantees that customers' storage accounts will have connectivity to its Internet gateway. Users can submit service claims for credit through customer service. Microsoft gives a 25% service credit for less than 99% monthly uptime and 10% for between 99% and 99.9% monthly uptime.

The full Storage service-level agreement (SLA) is available for download here. Microsoft does not offer custom SLAs.


Enterprise customers can monitor their storage accounts in the Windows Azure Platform Management Portal. They can specify the monitoring level and data retention policies for each cloud storage service associated with the storage account (Blob, Queue and Table). Users also have the option to customize their dashboards for both monitoring and management purposes.


Windows Azure gives users control of access keys and permits secure connections via HTTPS. Microsoft noted its compliance with applicable privacy laws and its adherence to the privacy practices outlined in the Microsoft Online Privacy Statement. In addition to data center, network and personnel security practices, Windows Azure incorporates various security practices at the application layer, as security and industry specialists have independently verified, according to Microsoft. Windows Azure Storage has ISO 27001 and SSAE 16/ISAE 3402 certifications. The company complies with EU Model Clauses and HIPAA Business Associate Agreement (BAA) requirements.

For user authentication, Windows Azure generates two 512-bit storage access keys when customers create an account. The keys are used for authentication when the storage account is accessed. According to Microsoft, by providing two storage access keys, Windows Azure enables customers to regenerate the keys with no interruption to their storage service or access to that service. Independent software vendors and enterprises can integrate with Active Directory to create more sophisticated authentication and authorization layers in their storage applications.

Additional notes

Customers can use Microsoft's Windows Azure application platform for the public cloud for many purposes other than data storage. Azure use cases include building Web applications, analyzing business data, and creating virtual machines for test and development or running SharePoint or other applications.

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