Scale-Out NAS: Best Practices to Implement Tomorrow’s Storage Today

Featured article by Stefan Bernbo, founder and CEO, Compuverde

As the data deluge continues on unabated, vertically scaling legacy approaches to storage are falling short. Organizations need to find a way to store high volumes of data without busting the budget, all while maintaining high levels of performance; they need to scale quickly and cost-effectively. With the wider acceptance of software-defined storage (SDS), scale-out storage solutions are becoming a reality in the data center.

Hybrid cloud is a cloud computing environment that uses a mix of on-premises, private cloud and public cloud services, with orchestration between the two platforms. Since hybrid cloud architectures are so new, many are still learning about the benefits and challenges associated with deploying a hybrid cloud approach. In this article, we go through some design elements you can use to ensure your hybrid cloud delivers the performance, flexibility and scalability you need.

The Need for Scale-Out NAS

At the heart of such a hybrid-cloud storage solution must be a scale-out NAS. Since hybrid cloud architectures are relatively new to the market—and even newer in full-scale deployment—many organizations are unaware of the importance of consistency in a scale-out NAS. Many environments are eventually consistent, meaning that files that you write to one node are not immediately accessible from other nodes. This can be caused by not having a proper implementation of the protocols, or not tight enough integration with the virtual file system. The opposite of that is being strictly consistent: files are accessible from all nodes at the same time. Compliant protocol implementations and tight integration with the virtual file system is a good recipe for success.

A scale-out NAS approach like this should be based on three layers. Each server in the cluster will run a software stack based on these layers.

– Layer 1 is the persistent storage layer, based on an object store, which provides advantages like extreme scalability. However, the layer must be strictly consistent in itself.

– Layer 2 is the virtual file system, the heart of any scale-out NAS. This layer handles features like caching, locking, tiering, quota and snapshots.

– Layer 3 contains the protocols like SMB and NFS but also integration points for hypervisors, for example.

It is very important to keep the architecture symmetrical and clean. If you manage to do that, many future architectural challenges will be much easier to solve.

Layer 1, the storage layer, now deserves closely scrutiny. Since it is based on an object store, we can now easily scale our storage solution. With a clean and symmetrical architecture, we can reach exabytes of data and trillions of files.

Because it is the duty of the storage layer to ensure redundancy, a fast and effective self-healing mechanism is needed. To keep the data footprint low in the data center, the storage layer needs to support different file encodings. Some are good for performance and some for reducing the footprint.

Where Does the Metadata Go?

Metadata is critical to the virtual file system. Metadata are pieces of information that describe the structure of the file system. For example, one metadata file can contain information about what files and folders are contained in a single folder in the file system. That means that we will have one metadata file for each folder in our virtual file system. As the virtual file system grows, we will get more and more metadata files

Though centralized storage of metadata is the preferred method for some users, it’s not practical for scale-out. So, let’s look at where not to store metadata. Storing metadata in a single server can cause poor scalability, poor performance and poor availability. Since our storage layer is based on an object store, a better place to store all our metadata is in the object store – particularly when we are talking about high quantities of metadata. This will ensure good scalability, good performance and good availability.

Have You Got Enough Cache?

In order to increase performance, SDS solutions need caching devices. From a storage solution perspective, both speed and size matter – as well as price; finding the sweet spot is important. For an SDS solution, it is also important to protect the data at a higher level by replicating the data to another node before de-staging the data to the storage layer.

Especially in virtual or cloud environments, it becomes more important to support multiple file systems and domains as the storage solution grows in both capacity and features. Supporting multiple file systems is also very important. Different applications and use cases prefer different protocols. And sometimes, it is also necessary to be able to access the same data across different protocols.

The Virtual World

In terms of the hybrid cloud, the “cloud” part of course needs support for hypervisors. Therefore, the scale-out NAS needs to be able to runs as hyper-converged as well. Being software-defined makes sense here.

In the case of a flat architecture that has no external storage systems, the scale-out NAS must be able to run as a virtual machine and make use of the hypervisor host’s physical resources. The guest virtual machine’s (VM) own images and data will be stored in the virtual file system that the scale-out NAS provides. The guest VMs can use this file system to share files between them, making it perfect for VDI environments as well.

Now, why is it important to support many protocols? Well, in a virtual environment, there are many different applications running, having different needs for protocols. By supporting many protocols, we keep the architecture flat, and we have the ability to share data between applications that speak different protocols, to some extent.

All these elements work together to create a highly flexible and useful storage solution: being software-defined, supporting both fast and energy-efficient hardware, having an architecture that allows us to start small and scale up, supporting bare-metal as well as virtual environments, and having support for all major protocols.

Hybrid Cloud

A common situation is one in which different offices have a need for both a private area and an area that they share with other branches. Each site has its own independent file system, so only parts of the file system will be shared with others.

Choosing a portion of a file system and allowing others to mount it at any given point in the other file systems provides the flexibility needed to scale the file system outside the four walls of the office – making sure that the synchronization is made at the file system level in order to have a consistent view of the file system across sites. Being able to specify different file encodings at different sites is useful, for example, if one site is used as a backup target.

Building for the Future

This is what the new model of hybrid cloud system looks like: efficient, clean, linear scaling that can accommodate exabytes of data. Multiple entry points clear up potential performance bottlenecks due to a single file system that spans all servers. Flexible scale-out is possible by adding nodes. There is flash support for high performance and native support of protocols. Affordable expansion is possible when a scale-out NAS is in place.

About the Author

Stefan Bernbo is the founder and CEO of Compuverde. For 20 years, Stefan has designed and built numerous enterprise scale data storage solutions designed to be cost effective for storing huge data sets. From 2004 to 2010 Stefan worked within this field for Storegate, the wide-reaching Internet based storage solution for consumer and business markets, with the highest possible availability and scalability requirements. Previously, Stefan has worked with system and software architecture on several projects with Swedish giant Ericsson, the world-leading provider of telecommunications equipment and services to mobile and fixed network operators.