Microsoft said Tuesday that it's going to buy privately held StorSimple and its Cloud-integrated Storage (CiS) solutions to advance its Cloud OS vision and help customers embrace hybrid cloud computing more efficiently.

It did not say what it's paying.

As a gauge, the start-up raised at least $31.5 million in VC funding from such companies as Ignition, a retreat of ex-Microsofties.

StorSimple is a partner of Microsoft's and its widgetry works with Windows.

It integrates cloud storage for on-premises applications and offers a single appliance delivering high-performance tiered local and cloud storage, live archiving, cloud-based data protection and disaster recovery.

Ironically, it also supports VMware and OpenStack, the latter by integrating with Rackspace's underlying Cloud Files.

StorSimple claims its cloud-as-tier architecture is 80% more cost-effective than traditional storage.

According to Microsoft's Server and Tools Division corporate VP Michael Park, "Customers faced with explosive growth in data are looking to the cloud to help them store, manage and archive that data. But, to be effective, cloud storage needs to integrate with IT's current investments. StorSimple's approach helps customers seamlessly integrate on-premises storage with cloud storage through intelligent automation and management."

StorSimple combines the data management functions of primary storage, backup, archive and disaster recovery with cloud integration. Features such as Cloud Snapshots and Cloud Clones enable instant restore and offsite data replication. Its Snapshots protect data in public clouds like OpenStack.

The widgetry automatically tiers deduplicated, compressed data and is supposed to offer additional security features in the cloud through data encryption and on-premise key management.

The company has been focused on large enterprises across vertical markets, including retail, oil and gas, manufacturing, consumer goods, healthcare, and financial services that have chosen Windows Azure as their primary cloud.