Fueled by Docker's rapid ascent, Linux containers have become a favored vehicle for applications. But running that application on a platform-as-a-service (PaaS) can be troublesome, because containers aren't fully data-aware. A database tied to the application, for instance, would have to be housed elsewhere.

The startup formerly known as Hybrid Cluster is taking on the challenge. Now renamed ClusterHQ, the company is releasing version 0.1 of its Flocker open-source software on Wednesday, claiming to fill a crucial gap when it comes to using Docker containers in production environments.

Flocker, which the company describes as a volume manager, gives Docker an ability to handle data and an awareness of state. "There are no tools today to do basic things like upgrade a database version without having downtime," says Michael Ferranti, ClusterHQ's vice president of marketing.

You could draw an analogy here to VMware's vMotion. Virtual machines were nice on their own, but they reached a new level of utility when it became possible to move them to new hosts. Flocker aims to likewise advance the cause of Linux containers — by making them portable, yes, but by allowing stateful operations as well.

So far, PaaS environments have been suitable for stateless applications — the kind that don't have to remember anything, in a sense. If an application requires access to data, then the database and its operations have to be hosted elsewhere. That's prevented many enterprise applications from moving to containers and PaaS hosting, Ferranti says. "Enterprises don't want to have to manage two platforms in order to run an application."

ClusterHQ could be come one of several companies that end up fleshing out the ecosystem around the open source containers. "Docker [Inc.] is a very young company, and despite their growth, they are focused on solving lower-level problems," such as the container technology itself and the fostering of an open-source community, Ferranti says.

ClusterHQ has worked on these problems before, with its Hybrid Cluster product for FreeBSD environments, but Docker and Linux containers have now won the market's heart. That's why the company is changing names — essentially relaunching itself — and putting its product efforts into Flocker. (The Hybrid Cluster product will continue to be supported but won't be the subject of further development, Ferranti says.)