Startup ClusterHQ today announced that it has teamed up with VMware to develop a storage driver that allows ClusterHQ’s Flocker open-source software to integrate with VMware’s vSphere server virtualization software.

The result is that companies can now provision storage for specific containers, not just virtual machines, with VMware storage software like Virtual SAN and vSphere Virtual Volumes.

Developers have flocked to container technologies like Docker as lightweight alternatives to longstanding virtual machine technology. ClusterHQ is one of many container startups, but it’s focusing on solving the specific problem of running stateful services that are constantly changing (such as databases) inside of containers.

ClusterHQ has previously partnered with other major storage vendors, including EMC and NetApp. But the partnership with VMware is especially meaningful, given that ClusterHQ chief executive Mark Davis sold his storage software company Virsto to VMware in 2013.

Plus, VMware is particularly interested in containers, as they represent competition for its flagship vSphere software, or at the very least a trendy technology to run on top of vSphere. So it’s an interesting announcement to kick off the 2015 VMworld conference in San Francisco, which begins today.

ClusterHQ started in 2008 and announced a 12 million funding round earlier this year. Flocker works with databases like MongoDB, MySQL, PostgreSQL, RabbitMQ, Redis, and Riak.

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