NAS vs SAN | Choosing the Right Storage Solution

Table of Contents

• What is SAN?
• What is NAS
• NAS + SAN = ?

Data is now an important part of our lives. And when it comes to dynamic data growth, security, and storage, there are different strategies adopted by users, depending on the size and importance of the data. Today we will consider two of them – NAS and SAN – and answer the question of which one is better to choose.

What is SAN?

Today, when we talk about enterprise-level storage, we mean network storage (storage networking). More known to the general public are storage networks – SAN (storage area network). A SAN is a dedicated storage network that allows multiple servers to share a single external storage resource without overburdening the local area network.

SAN is media agnostic, but fiber channel (FC) technology is now the de facto standard, providing data transfer rates of 1-2 Gbps. Unlike traditional SCSI-based transmission media, which provide a connection distance of no more than 25 meters, Fiber Channel allows you to work at a distance of up to 100 km. The transmission medium in a Fiber Channel network can be both copper cable and optical fiber.

A storage network can connect RAID disk arrays, simple disk arrays, and tape or magneto-optical libraries for data backup and archive.

The goal of SAN software is primarily to centrally manage the storage network, including configuration, monitoring, control, and analysis of network components. One of the most important is the function of managing access to disk arrays if heterogeneous server data is stored in the SAN. SANs allow multiple servers to simultaneously access multiple disk subsystems by tying each host to specific disks on a specific disk array.

The appeal of storage networks comes from the benefits they can bring to organizations demanding efficient handling of large volumes of data. A dedicated storage network offloads the main (local or global) network of computing servers and client workstations, freeing it from data input/output streams.

This factor, as well as the high-speed transmission medium used for the SAN, improves the performance of data exchange processes with external storage systems. SAN means the consolidation of storage systems, the creation of a single pool of resources on different media, which will be shared by all computing power, and as a result, the required external storage capacity can be provided by fewer subsystems.

Consolidated SAN storage is more scalable because it allows storage capacity to grow independently of servers and without interrupting their operation. Finally, SAN allows centralized management of a single pool of external storage, which simplifies administration.

Of course, SANs are not a cheap and difficult solution, and although all the leading vendors are releasing Fiber Channel SAN devices today, their compatibility is not guaranteed, and choosing the right equipment creates a problem for users. There will be additional costs for dedicated networking and management software, and the initial cost of a SAN will be higher than storage with DAS, but the total cost of ownership should be lower.

What is NAS?

Unlike SAN, NAS (network-attached storage) is not a network, but a network storage device, more precisely, a dedicated file server with a disk subsystem connected to it. Sometimes the NAS configuration may include an optical or tape library. A NAS appliance connects directly to the network and provides hosts with access to files on its integrated external storage subsystem.

A NAS device resembles a DAS configuration but is fundamentally different in that it provides file-level access rather than data block-level access and allows all applications on the network to share files on their drives. The NAS specifies a file in the file system, an offset in that file (which is represented as a sequence of bytes), and the number of bytes to be read or written.

The request to the NAS device does not determine the volume or sector on the disk where the file is located. The task of the operating system of the NAS device is to translate access to a specific file into a request at the level of data blocks. File access and the ability to share information are useful for applications that need to serve many users at the same time but do not require very large amounts of data to be downloaded on each request. Therefore, it is becoming common practice to use a NAS for Internet applications, Web services, or CAD, where hundreds of people work on a single project.

The NAS option is easy to install and manage. Unlike a storage network, installing a NAS device does not require special planning and the cost of additional management software – just connect the file server to the local network. The NAS relieves servers on the network of storage management tasks but does not offload network traffic because the communication between the general-purpose servers and the NAS is on the same local network.

A NAS device can be configured with one or more file systems, each with a specific set of disk volumes. All users of the same file system are allocated some disk space on demand.

Thus, NAS provides more efficient organization and use of memory resources compared to DAS, since the directly connected storage subsystem serves only one computing resource, and it may happen that one server on the local network has too much external memory, while the other is running out of disk space. However, multiple NAS devices cannot form a single pool of storage resources, and therefore an increase in the number of NAS nodes in the network will complicate the management task.

Details of NAS + SAN =?

Which form of storage infrastructure to choose: NAS or SAN? The choice SAN / NAS depends on the capabilities and needs of the organization, but it is fundamentally wrong to compare or, even more so, to oppose them, since these two configurations solve different problems.

File access and information sharing for applications on heterogeneous server platforms on a local area network are NAS. High-performance block database access and storage consolidation guarantee its reliability and efficiency – this is SAN.

In life, however, everything is more difficult. NAS and SAN often already co-exist or need to be implemented simultaneously in a company’s distributed IT infrastructure. This inevitably gives rise to problems of management and optimal use of storage resources.

Today, manufacturers are looking for ways to combine both technologies into a single network storage infrastructure that will provide data consolidation, and backup centralization, and simplify overall administration, scalability, and data protection. The convergence of NAS and SAN is one of the most important recent trends.