The modular solution of separate control and data planes of LINBIT® has many advantages. Still today, many storage systems have a monolithic design that combines the control plane and the data plane into a single application and a single protocol.
What is a Control Plane or a Data Plane?
The most important task that any storage system must perform is providing access to the storage volumes used for various workloads. For example, databases, file servers or virtualization environments. This is what we refer to as the data plane – all the components that are necessary to actually get data from the storage to the user and from the user to the storage.
Another task is the management of the configuration of storage volumes, which we refer to as the control plane. There is a rise of more dynamic systems like containerization, virtualization and cloud environments, and the associated software-defined storage systems. In such systems, storage volumes are frequently reconfigured, and this task is becoming increasingly important.
Why It‘s Important: Availability
If you need to shut down part of your infrastructure, because you are updating hardware, for instance, it is essential when the most fundamental services remain available. Storage is probably one of those fundamental and important services since most other systems rely on it.
A storage system with a modular design that provides independent control. And data planes bring your infrastructure one step closer to high availability.
Separate Control & Data Planes
Many storage systems can only provide access to storage volumes if all their subsystems are online. The design may even be utterly monolithic so that the management functions. And a single application that uses a single network protocol contains the storage access functions.
In LINBIT’s DRBD® storage systems, only the most fundamental control plane functions are tightly coupled with the data plane and the operation of storage volumes. The LINSTOR storage management software provides high-level control functions, like managing storage volumes and their configuration, managing cluster nodes, or providing an automatic selection of cluster nodes to create storage volumes. These two components, DRBD and LINSTOR®, are fundamentally independent of each other.
DRBD storage volumes, even those managed by LINSTOR, are accessible even if the LINSTOR software is unavailable. Therefore, the LINSTOR software can be shut down, restarted or upgraded while users retain access to existing storage volumes. While it is less valuable, the same is true the other way around. LINSTOR controllers that don‘t rely on DRBD storage continue to service storage management requests. This is true even if the storage system itself is unavailable. The changed configuration will simply be applied whenever the actual storage system is online again.