NAS: Eliminating The Server-Based Stranglehold On File Serving.

If one thing is clear in the ever-changing, complex world of computer storage, it is that users have many more options today than they did five years ago. In the 1980s, storage joined servers and networking as the third pillar of the IT world. This focus on storage has left us with no less than 200 vendors offering storage solutions in a number of different categories. With this broad selection, how does an IS manager make sense of SANs, NAS, and other types of storage subsystems?

The cost and complexity of SANs and high-end storage subsystems have narrowed the applicability of these architectures to top dollar, mission-critical applications. However, the debate between server-based storage (SBS) and network-attached storage (NAS) is just heating up. Despite the attention given to email and web serving requirements, the most common application for storage in the SBS and NAS arenas is general file serving, or client-based storage needs. This article discusses the cost, manageability, and flexibility tradeoffs an IS manager must consider when evaluating the deployment of SBS and NAS for file serving applications.

Server-Based Stranglehold 

Primarily because there were no other reasonable choices available for file serving until recently, most of the shared network storage deployed today is server based--as high as 92 percent according to IDC. Captured and direct attached are the two main types of server-based storage.

Captured storage is the storage inside of the server. While the capacity of server-captured storage has grown significantly, at the same time, server form factors are shrinking--it is still limited in its ability to scale by the number of available expansion slots.

Direct-attached storage provides much more scalability, but can sometimes be limited by performance issues. As the storage grows, the strain on the server to handle all processing and I/O can quickly consume system resources.

While SBS can sometimes offer great price points and advanced features, ultimately it will require the addition of more servers to provide more capacity. Each new server brought into the environment requires management, increasing the workload on already strained IS staff.

NAS Emerges

NAS is not a new concept--it has been around for almost ten years. It has, however, recently emerged as a mature technology targeted predominantly at file serving. NAS is also becoming the back-end storage of choice for some applications, showing that it is an effective solution for a wide range of storage needs.

Why has NAS begun to eat away at the market opportunity previously dominated by SBS? There are three main reasons: it is cost-competitive, it is easier to manage, and it gives administrators more flexibility in storage deployment and redeployment. In comparing these three features, there is a strong case to be made for NAS to displace a good deal of the SBS now commonplace throughout organizations.

Adding Up The Real Cost Of Storage: Initial Costs And Manageability

Cost is not simply money spent on the actual storage system itself. IDC estimates that 80 percent of the total cost of storage is centered around storage management--the amount of time spent by skilled IT staff required to keep often complex storage systems running smoothly. Total cost of storage consists of hardware investment, management costs, and downtime or productivity costs.

The actual cost of NAS and most server-based storage is about the same--ranging from 2 cents per MB to more than 30 cents per MB. Once both solutions are purchased and installed, they offer similar functionality. The real difference comes in configuring, deploying, and managing the storage.

With server-based storage, there are often additional software costs, particularly for operating systems and utilities. Conversely, NAS products come pre-configured with the operating system and all associated software. Server-based storage also requires the administrator to install the software and configure the box. This takes time, which again means money. Adding storage to SBS also requires that the server be taken offline, and in some cases, a significant amount of reconfiguration may be necessary.

All of these factors contribute to the escalating cost of server-based storage--particularly apparent when storage needs are growing rapidly. NAS can offer significant improvements over server-based storage, most significantly in terms of reducing the 80 percent cost attributed to management.

Flexible Storage Deployments For Mixed Environments

A major benefit of NAS is its support of multiple client file systems. Few organizations have standardized across the board on either Windows or Unix, leaving IS to support mixed environments. In a server-based storage scenario, a dedicated server is required for each protocol. If engineering is using a CAD/CAM application while the rest of an organization is using Windows Office applications, the IT group must support two independent file servers.

Most NAS systems support multiple operating environments, some even allowing file sharing on the same device. For customers, this means flexibility, as cross-platform NAS not only provides standardization of file services, but can also lead to cost savings in staffing, training, and deployment.

Target New Deployments For NAS Trials

Though the benefits of NAS are frequently well understood, the large existing installed base of file servers is still a significant barrier to NAS deployment. It is said that old storage never really dies, it just gets redeployed. Rather than replacing SBS, IS managers need to look at new storage deployments as opportunities to incorporate different storage technology. New projects, new workgroups or departments, and new applications are all opportunities to implement NAS.

If IS does decide to migrate data from existing SBS to NAS, a great deal of planning is required. Downtime must be scheduled, and then data must be backed up and moved to the new server. In this case, the cost, manageability, and storage sharing benefits of NAS provide the incentive to invest in the new technology.

NAS offers many opportunities for IS managers to reduce their total cost of ownership by eliminating many of the management costs associated with storage. The benefits are particularly relevant in file serving, the most common corporate application for storage. IS managers face stiff challenges in deciding when and how to migrate their server-based storage to NAS--often finding it easier and more economical to use NAS for storage expansion rather than storage replacement.

As NAS products mature, and features and options continue to improve, look for NAS to become a mainstay of an overall storage strategy. The cost savings inherent in a NAS architecture make it a matter of time before NAS displaces SBS as the primary storage vehicle for sharing information in a networking environment.

Greg Dahl is the vice president of marketing and business development at Tricord Systems (Plymouth, MN).