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NAS Versus SAN: Can You Still Tell the Difference?

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By: Ivan Schneider (11/10/2010)

Newcomers to enterprise networks may be excused if they are confused by the terminology of SAN and NAS. Network Attached Storage, or NAS, refers to storage devices that you could plug into a network that could be made accessible to other devices on that network. To access data through a NAS, you make a request through the file-handling capabilities of your operating system. The request goes through the network to the NAS, and then the NAS device handles the request through its own file system. This takes longer than accessing a disk natively at the block level. Therefore, your PC typically recognizes NAS as an external, networked device. Lacking block-level access to the NAS device, NAS storage has long been considered an imperfect replacement for local storage, lacking suitability for high-performance applications requiring rapid throughput and response times. Storage Area Network, or SAN, encompasses enterprise-class technology that creates a pool of block-level storage accessible through fast, fiber-optic cables as native storage to an application. There’s no intermediary file system between you and the SAN, and so requests for storage are much faster. On a SAN, you can run enterprise applications with greater assurance, resiliency, and protection. And so NAS is file-level storage and SAN is block-level storage. What’s so hard to understand about that? The tricky part of understanding these technologies is that their acronyms share two of the same letters, with those letters standing for the same words. However, the confusion index has risen with the latest technological advancements in storage that make NAS faster and more reliable, while also making SAN easier to implement and more flexible across platforms. One of the knocks against NAS is that it’s too slow. But as networks and NAS devices get faster, applications that may not have worked in previous generations of NAS devices may now work fine for a broader class of applications, such as streaming video. Similarly, one of the drawbacks of SAN is that it’s too complicated for some shops. You have to mix and match various components, from storage devices to routers and switches, and establish various protocols in tune with your existing networks. But even this has been changing, with technology vendors shipping units that embody enterprise-ready design patterns and architectures, for easier out-of-the-box deployment. From these trends, it’s becoming easier for firms to address their storage requirements at lower cost, greater capabilities, and higher levels of availability. Yet the storage story is far from over. Let’s say that NAS is the new JBOD (Just a Bunch of Disks), because of the combination of low cost and apparent speed using today’s NAS hardware. And SAN is the new NAS, because of the improved ease of configuration and installation of SAN, plus the ability to add geographic dispersion and automatic replication to data contained within a SAN. In that case, what’s the new SAN? To answer that question, let’s return to the concepts of file-level and block-level access. The relative disadvantage of NAS was that it only provided file-level access, making it necessary to perform additional calculations to access block-level data. Now consider a device that provides direct access to data through the application layer rather than via block-level access or file-level access. To retrieve or store information, you have to use a specific application on your own network. That application communicates to an intermediary application on the device itself, which in turn accesses the device’s file system and data blocks, and then returns a result. Thus, there are two levels of translation that have to occur within application-level storage schemes, making it slower than both NAS and SAN. Yet just as increased networking and processing speeds have increased the ability of NAS to operate at high levels, so too will faster computing enable these application-level storage capabilities. You’ve probably heard these capabilities described as “cloud computing,” a term that in my opinion covers too broad of an area to be truly useful. And so, when you’re looking at an application delivered using cloud technology, ask yourself at which layer it provides an entry point to your data. For example, if you’re accessing an Amazon S3 storage container, you’re establishing file-level connectivity, which should be familiar territory if you’ve been using NAS. Or, if you’re being told that some new application works via the cloud, remember that you’re going to have to access that data through several intermediary steps. These distinctions have implications not only for your throughput and retrieval speeds, but also for disaster recovery, business continuity planning and vendor management. By entering conversations about new technologies with a solid grounding in the capabilities and strengths of your on-the-ground storage technologies such as SAN and NAS, you’ll be in a good position to evaluate the technological offerings of tomorrow’s technologies.

Newcomers to enterprise networks may be excused if they are confused by the terminology of SAN and NAS.

Network Attached Storage, or NAS, refers to storage devices that you could plug into a network that could be made accessible to other devices on that network. To access data through a NAS, you make a request through the file-handling capabilities of your operating system. The request goes through the network to the NAS, and then the NAS device handles the request through its own file system. This takes longer than accessing a disk natively at the block level. Therefore, your PC typically recognizes NAS as an external, networked device. Lacking block-level access to the NAS device, NAS storage has long been considered an imperfect replacement for local storage, lacking suitability for high-performance applications requiring rapid throughput and response times.

Storage Area Network, or SAN, encompasses enterprise-class technology that creates a pool of block-level storage accessible through fast, fiber-optic cables as native storage to an application. There’s no intermediary file system between you and the SAN, and so requests for storage are much faster. On a SAN, you can run enterprise applications with greater assurance, resiliency, and protection.

And so NAS is file-level storage and SAN is block-level storage. What’s so hard to understand about that? The tricky part of understanding these technologies is that their acronyms share two of the same letters, with those letters standing for the same words.

However, the confusion index has risen with the latest technological advancements in storage that make NAS faster and more reliable, while also making SAN easier to implement and more flexible across platforms.

One of the knocks against NAS is that it’s too slow. But as networks and NAS devices get faster, applications that may not have worked in previous generations of NAS devices may now work fine for a broader class of applications, such as streaming video.

Similarly, one of the drawbacks of SAN is that it’s too complicated for some shops. You have to mix and match various components, from storage devices to routers and switches, and establish various protocols in tune with your existing networks. But even this has been changing, with technology vendors shipping units that embody enterprise-ready design patterns and architectures, for easier out-of-the-box deployment.

From these trends, it’s becoming easier for firms to address their storage requirements at lower cost, greater capabilities, and higher levels of availability.

Yet the storage story is far from over.

Let’s say that NAS is the new JBOD (Just a Bunch of Disks), because of the combination of low cost and apparent speed using today’s NAS hardware. And SAN is the new NAS, because of the improved ease of configuration and installation of SAN, plus the ability to add geographic dispersion and automatic replication to data contained within a SAN.

In that case, what’s the new SAN?

To answer that question, let’s return to the concepts of file-level and block-level access. The relative disadvantage of NAS was that it only provided file-level access, making it necessary to perform additional calculations to access block-level data. Now consider a device that provides direct access to data through the application layer rather than via block-level access or file-level access. To retrieve or store information, you have to use a specific application on your own network. That application communicates to an intermediary application on the device itself, which in turn accesses the device’s file system and data blocks, and then returns a result.

Thus, there are two levels of translation that have to occur within application-level storage schemes, making it slower than both NAS and SAN. Yet just as increased networking and processing speeds have increased the ability of NAS to operate at high levels, so too will faster computing enable these application-level storage capabilities.

You’ve probably heard these capabilities described as “cloud computing,” a term that in my opinion covers too broad of an area to be truly useful.

And so, when you’re looking at an application delivered using cloud technology, ask yourself at which layer it provides an entry point to your data. For example, if you’re accessing an Amazon S3 storage container, you’re establishing file-level connectivity, which should be familiar territory if you’ve been using NAS. Or, if you’re being told that some new application works via the cloud, remember that you’re going to have to access that data through several intermediary steps. These distinctions have implications not only for your throughput and retrieval speeds, but also for disaster recovery, business continuity planning and vendor management.

By entering conversations about new technologies with a solid grounding in the capabilities and strengths of your on-the-ground storage technologies such as SAN and NAS, you’ll be in a good position to evaluate the technological offerings of tomorrow’s technologies.