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Control and Data plane Linstor

The advantage of separate control and data planes

Many storage systems have a monolithic design that combines the control plane and the data plane into a single application and a single protocol, but LINBIT’s more modular solution comes with a number of advantages.

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 that are 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 is what we refer to as the control plane . With the rise of more dynamic systems like containerization, virtualization and cloud environments, and the associated software defined storage systems, where storage volumes are frequently reconfigured, this task is becoming increasingly important.

Data and Control plane Linstor

Why it is important: Availability

If you need to shut down part of your infrastructure, because you are updating hardware, for instance it is important when the most fundamental services remain available. Storage is probably one of those fundamental and important services, since most of the other systems rely on it.

A storage system with a modular design that provides independent control and data planes brings your infrastructure one step closer to high availability.

Independent control and data plane

Many storage systems can only provide access to storage volumes if all of their subsystems are online. The design may even be completely monolithic, so that the management functions and the storage access functions are contained within a single application that uses a single network protocol.

In LINBIT’s DRBD-based storage systems, only the most fundamental control plane functions are tightly coupled with the data plane and the operation of storage volumes. High-level control functions, like managing storage volumes and their configuration, managing cluster nodes, or providing automatic selection of cluster nodes for the creation of storage volumes, are provided by the LINSTOR storage management software. These two components, DRBD and LINSTOR, are fundamentally independent of each other.

DRBD storage volumes, even those that are managed by LINSTOR, are kept accessible even if the LINSTOR software is unavailable. This means that the LINSTOR software can be shut down, restarted or upgraded while users retain their access to existing storage volumes. While it is less useful, the same is even true the other way around: a LINSTOR controller that does not rely on storage provided by DRBD and will continue to service storage management requests even if the storage system itself is unavailable. The changed configuration will simply be applied whenever the actual storage system is online again.

Robert Altnoeder on Linkedin
Robert Altnoeder
Robert joined the LINBIT development team in 2013. He had worked with
DRBD at a startup company in the SaaS field before joining LINBIT. His
current primary field of work is the architecture and implementation of
LINSTOR, the cluster management component of LINBIT's SDS software.

Testing SSD Drives with DRBD: Intel DC 3700 Series

Over the next few weeks we’ll be posting results from tests that we’ve run against various manufactures SSD drives; including Intel, SanDisk, and Micron, to name a few.

The first post in this series goes over our findings of the Intel DC S 3700 Series 800GB SATA SSD drives. Read more