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SAN vs. NAS: A diagram of the differences

Having trouble choosing a storage system? While there are some basic differences between SAN and NAS, there are also nuances to consider when making your choice.

SAN and NAS are storage system staples, and while they may appear similar at a glance, they are not interchangeable. There are many factors to consider when deciding whether to use SAN vs. NAS, so the answer isn't the same for every organization. However, by looking at the benefits and drawbacks of each, you should be able to choose the right data storage system for your organization.

Generally speaking, if your application requires block I/O or if there is a significant performance requirement, use a storage area network. If your application uses file-based I/O or if you need to share files and you want simple administration, network-attached storage would be the best option.

While that's a good rule of thumb for knowing where to use each system, there are nuances to each approach and to every use case. Below, with the help of some simple visuals, we will outline the differences between SAN vs. NAS, how each system works and where it works best.

SAN

A SAN is a dedicated high-speed network that interconnects and presents shared pools of storage to servers. A SAN is an independent storage network that enables high performance and access to storage similar to how direct-attached storage (DAS) works. There are three components to a SAN: cabling, host bus adapters (HBAs) and switches.

HBAs used for storage are typically protocols such as Fibre Channel (FC) or Serial-Attached SCSI. Ethernet-based iSCSI is another protocol option that small and midsize organizations more commonly use.

In a SAN, the switch connects servers and shared pools of storage. An FC switch is most often used in a SAN, because it is compatible with the FC protocol and is designed for high performance and low latency. Ethernet switches are also common.

SANs can be managed centrally and send out block storage-based access requests for a data storage device.

A SAN can be used for distributed applications, thanks to speedy local network performance and high availability for applications. Because IT administrators can offload storage functions and separate storage networks, a SAN offers improved performance over storage systems that aren't as structured or scalable.

Using a SAN enables admins to tier storage and consolidate resources, and a SAN is generally considered a secure storage system. All of these benefits also contribute to the drawbacks of using a SAN: cost and complexity. The hardware involved with building a SAN comes with a high price tag, and its implementation requires specialized services, which will add to the bill. Also, FC is a protocol developed specifically for storage and is more expensive than common network protocol Ethernet, so FC SANs will increase the price even more.

SAN vs. NAS

NAS

NAS is also a network-based storage system, but unlike a SAN, NAS uses dedicated file storage. NAS enables users and client devices to get data from a centralized disk. NAS devices are typically managed like a browser, and they don't have a keyboard or display.

NAS connects to an Ethernet network through a switch, and protocols include Network File System (NFS) and server message block (SMB).

Using a NAS enables users to share data and collaborate easily and effectively. Teams that have users working remotely or in different time zones particularly benefit from NAS, which connects to a wireless router and is accessible to distributed work environments. As long as a device is connected to the network, a user can easily access the files residing on the storage network.

NAS resides on a LAN. NAS nodes are independent on the LAN, and each has a unique IP address. Because of the collaborative nature of NAS, it is commonly deployed as the foundation for a cloud storage system.

One major factor to consider in the SAN vs. NAS debate is cost. Along with its accessibility and high capacity, NAS is a relatively low-cost data storage system. NAS devices typically come with minimal components to maintain and manage. Of course, cost will vary by size and scope, so keep that in mind when looking into NAS. NAS systems can be designed for home offices and smaller businesses, as well as enterprises.

Major differences between the two

At a basic level, SAN is more similar to DAS than NAS, because it uses block storage. NAS works as a remote system, where file requests are redirected over a network to a NAS device.

If your organization deals with large amounts of unstructured data, NAS might be a better option. If performance is your priority, SAN is the better option.

While NAS is designed to handle unstructured data, SAN is used primarily for structured data that has been organized and formatted inside a database. Unstructured data is increasingly common today, however, thanks to massive amounts of data coming from sources such as videos, audio files, photos and medical images that do not get consolidated and organized the way structured data does. If your organization deals with large amounts of unstructured data, NAS might be a better option.

If performance is your priority, SAN is the better option. While the file system of NAS tends to result in lower throughput and higher latency, SAN is well suited to high-speed traffic. Scalability is another point in SAN's corner; the architecture of a SAN enables scaling up or scaling out capacity and performance. While higher end enterprise NAS can be highly scalable, entry-level NAS is not.

As we mentioned earlier, there are a lot of differences between NAS and SAN when it comes to cost. A SAN is not only more expensive than a NAS from the start because of its high-priced hardware and specialized services, but its complexity makes maintenance and management a great deal more costly as well. NAS deployment consists of plugging into the LAN, while a SAN means adding hardware and often bringing in administrators specialized in managing the network.

Using SAN and NAS together

At this point, you may be looking at the benefits of both SAN and NAS wondering why you can't use them together. Some businesses do just that. Rather than debate SAN vs. NAS, these organizations use a combination of the two network types -- sometimes, in the same multiprotocol storage array. The two systems can complement each other and meet different needs within the organization.

To add NAS to a SAN, a NAS gateway can be used to support both systems. A NAS gateway is a NAS system that externally attaches storage media, usually over an FC interface. This gives the IP network access to the SAN's block-level storage, while processing client requests through NFS and SMB sharing protocols. But many mainstream SAN arrays now support files without requiring a NAS gateway.

NAS gateway

Combining the SAN and NAS storage systems through a NAS gateway will add scalability and performance and the best of both SAN and NAS worlds. A NAS gateway keeps costs down when consolidating the storage systems and is not limited by the storage capacity like a traditional appliance.

Editor's note: This article was expanded and updated in June 2019.

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