SAN vs. NAS:: The Critical Decision

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SAN Critical vs. NAS:Decision The Executive Summary The storage strategy for your organization is dictated by many factors: factors: the nature of the documents and files you need to store, the file usage patterns required to support your business operations, the scope and scale sc ale of your business and your infrastructure, frastruc ture, and of course, your IT budget. The budgetary factor encompasses not only equipment but has al soaccess also maintenance and management costs. Youthey need to ensure that yourcosts, business to the documents they need when need them in a way that is flexible, scalable sc alable and straightforward to operate and manage. Among the myriad decisions deci sions you’ll have to make as you outline your infrastructure and storage strategy is the decision between a storage area network (SAN) and network attached storage (NAS). (NAS). The factors affecting that decision have changed, as both SAN and NAS technology has evol evolved, ved, transmission protocols and capabilities have evolved, virtualization has become a major factor, factor, and new usage cases have emerged including storage support for private cloud environments. Still, this is as much a business decision as a technology decision. The primary factors must be the business needs and goals.

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vs. NAS: The Critical Decision


Introduction   Introduction There are perennial choices in life— coffee or tea, Coke or Pepsi, paper or plastic. For CIOs and IT decisionmakers, the decision to deploy and use a storage area network (SAN) or network attached storage (NAS) ranks

The SAN vs. NAS choice is all about choosing the technology that best supports your existing strategy and longer-term business goals. You must ensure that what you choose to deploy and the manner in which it’s deployed fully sup-

right up there. Choosing between a SAN, NAS, or some combination of the two technologies is a major aspect of determining the structure of your storage environment.Decisions you make today will impact how your organization’s data is stored, how your business users access that data, the extent and source of your ongoing management costs, and the lifecycle of data throughout your organization. Take a careful look at your overall business processes and how your data management into thoseis processes. Thestrategy SAN vs.fits NAS choice all about choosing the technology that best supports your existing strategy and longer-term business goals. You must ensure that what you choose to deploy and the manner in which it’s deployed fully supports that strategy. To choose the technology that will best support your organization’s business goals and business processes, it is essential to understand both technologies, their similarities and differences, and the type of storage and access for which both are best suited. In a nutshell, a SAN is a network of multiple devices best suited for block-level storage. A NAS device is a single storage unit best suited for file-level storage. Here are the characteristics of both:

ports that strategy. • Can control access to to particular sets of applications orusers  

Network-Attached Storage   (NAS) • File-level data storage connected directly to network • Network Networked ed appliances consisting of hard drive or hard drive array • Often configured specific specifically ally for file-sharing • Lets you you add more storage, or perform maintenance without shutting down

stant access to large blocks of data. These applications perform frequent read and save operations, like databases, email, and finance applications. “SANs are really great for blocklevel applications like SQL Server or Exchange; applications that have a heavy I/O load,” says Nicholas Rose, Dell Computer Corporation storage program manager. That is not the only function for which SANs are configured, configu red, however. As SAN technology has evolved, it has become more feature-rich. Most SANs can now support not only the data storage and access needs of enterprise, block-level applications. They can also help IT establish automated backup and recovery processes. Modern SANs are also capable of supporting sophisticated storage functions like disk mirroring, archiving and retrieval, data migration from one device to another, and data sharing among network servers. These capabilities and the ability to automate most functions helps IT make business processes more efficient. This can help the CIO turn around perceptions of IT as a cost center and make it operate as a profit center. While SANs are sub-networks of different storage devices all working together to consolidate and automate block level storage, NAS are individual

• Dedicated network of multiple hard disk arrays • Store Storess consolidated, contiguous block-level data

While both provide flexible and scalable storage, SAN and NAS by their very nature are best designed to support different business needs and different processes. As a SAN operates

devices that provide file-level storage. They are suitable to replace or to consolidate separate file servers. NAS provides both the storage and a file management system, so they can provide access to specific sets of files or specific sets of users. A CIO could, for example, have a NAS set up specifically for the legal department. Another NAS could be configured and provide access to the accounting department. In this way, storage and file access could be com-

• Servers can access access data stored on networked devices

on storage,needing it is bestcons uited suited for block-level larger applications

partmentalized by business function. To a certain extent, NAS devices are

Similarities and Differences   Storage Area Network (SAN)

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relatively simple to set up and maintain. They let you you add more storage space without having to shut down the network. You can also perform maintenance and upgrades to select devices independently. A NAS device does not have to be connected to a

NAS lies at the communication protocol level. NAS devices communicate through NFS or CFS over a network I/O built on Fibre or iSCSI. Fibre channel is well-suited for delivering data in block levels. A SAN does not have to use Internet connections

While both SANs and NAS devices centralize data, NAS devices can let users share data as single files in a single data repository. NAS devices identify and transfer data by file name, while a SAN addresses data by block identifier and transfers data in complete blocks.

server, but can be located anywhere on the network. A NAS, or series of NAS devices, really cannot replace a SAN, however. however. While you could add a significant number of NAS devices to a network, they would reach a point where they would become a challenge to manage. A group of NAS devices can become cumberc umbersome if there are too many attached to the same network. While it is i s relatively easy to establish protocols and access control for individual NAS devices,

or IP for data transfer, which reduces latency and greatly g reatly improves performance. That is why SAN systems are well-suited for I/O intensive applications like databases and email. Beyond costs and data delivery, the functional tradeoff between SAN and NAS remains speed and data throughput. The communication protocols continue to evolve, however, which affect the equation. The iSCSI and Fibre Channel over Ethernet protocols both promise to change the storage land-

Besides the lower acquisition and management costs, NAS devices can operate and communicate over an existing IP network. SANs are capable of doing that as well, using iSCSI protocol. As Gartner states in its Midmarket Report, “Use a NAS where you can, and a SAN where you must.” The Gartner report urges careful consideration, stating that not every application will require a SAN, even large storage implementations.

doing the same convoluted. for a large number of them becomes Depending on network throughput, they could also become a performance bottleneck. Both a SAN and NAS support their own sets of networking protocols p rotocols for access control. Besides block-level vs. file-level access, another of the basic technical differences between SAN and

scape. Theover iSCSI protocol transmit SCSI data standard IPcan networks, so it can be used virtually anywhere and provides high speed performance. Fibre Channel over Ethernet is a proposed standard that will let Fibre Channel transmissions do the same. The speed and ability to use use existing infrastructure will make this a strong contender contender..

Business Benefits of SAN With its high speed, block-level data access capabilities, SANs are exceptional for business-critical, always-on applications like accounting, financial reporting systems, databases, and email. These enterprise-grade applications need constant access to large

As Gartner states in its Midmarket Report, “Use a NAS where you can, and a SAN where you must.”

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vs. NAS: The Critical Decision


blocks of data to operate efficiently. Because a SAN stores data on dedicated storage arrays, it optimizes your server processing power for those heavy workload and business-critical applications. You can also provision storage capacity to individual servers or

new problems there. It lowers whole idea of management of the array. You can easily outgrow your array. You need to be aware of what is going on.” SANs help consolidate data storage and regulate access with multiple protocols. This consolidation low-

storage,” says Rose. “Everyone in business will have some sort of file-level server for storing frequently accessed documents and PDFs. Instead of file servers, it might make sense to have NAS. You can shrink that file server environment down to one or two

applications, which helps further optimize your overall processing power. p ower. Furthermore, the block-level storage facilitated by SAN makes it easier for you to expand. This helps facilitate growth, and gives you a flexible and scalable scalabl e storage network. The configuration of a SAN and the manner in which it operates can also improve your data security and protection. You can carefully controlaccess to all or certain portions of your data. Some of the most effective usage

ers cost and simplifies management. This works not only in the physical environment, but also when SANs are handling storage and data access for virtual environ environments. ments. There have been other changes in the industry as well that have manifested themselves in the SAN vs. NAS debate. Most notably is the dramatic increase in I/O capacity. The fiber industry has grown very strong. Protocols are also advancing in capacity (in terms of how much data they can

devices. The cost savings are great [in terms of reducing both equipment acquisition and management costs].” Some of the tangible benefits of NAS devices include scalability (the ability to continue to add additional devices), recoverability, security, performance, availability. They also operate efficiently and make efficient use of existing resources, typically have a lower total cost of ownership, centralize data management and backup, they’re easy to operate and manage,

cases for SANs areand storage consolidation, data centers, managing and protecting data flow between virtual machines and virtual servers. This has been the major paradigm shift in storage in recent years. “We’ve gone from traditional storage to virtual storage,” says Rose. “Instead of figuring out where data lives on the disk, just let the array handle it. You don’t have to spend 50 hours planning your storage.” The ever-expanding network of not only physical servers but virtual serv-

pass). All these changes up tostoran increasingly capable andadd flexible age environment, and a constantly changing picture of storage management. The iSCSI protocol has outgrown even the Fibre Channel market in terms of throughput capacity. It has grown from 1GB up to 10GB and 40GB. There is the possibility it will grow to even 100GB in the future.

andNAS provide faster data access. devices have their own file systems, and each device operates independently. File-level protocols transfer data from storage devices to servers as files. NAS devices are best used u sed with native data transfer protocols, like some special protocols VMware has developed for data transfer among its virtual machines and virtual servers. NAS devices can store and help you manage data up to the terabyte level. As your data storage needs expand, you can continue to add NAS devices

ers is driving dr iving that move. “Virtualization is a driving factor,” says Rose. “Everyone is talking about virtualization. virt ualization. It’s flattening the infrastructure.” This new paradigm does not come without its new management challenges. “There’s a whole new host of problems that arise with virtualization and managing that infrastructure,” infrast ructure,” he says. “Virtual server networks require management on the back end to ensure you’re running your environment correctly. Before it was all physical,

sive than SAN. They also use existing network resources, instead of requiring more costly access to fibre channel, although higher end NAS devices can use Fibre Channel as well. Small implementations of a few nodes are relatively simple to configure. However, as you continue to add additional NAS devices, the interconnectivity complexities increase which will necessitate additional management. NAS devices provide an efficient means of sharing a large repository

to your network. While that scalability and ease of adding additional devices is indeed a benefit, it can reach a point of ineffectiveness. While file management and user access control are simplified, NAS devices can potentially create a bottleneck from a performance standpoint.

now we’re virtualizing storage arrays as well. With virtual servers, there are

of individual individual users.“NAS is files reallyamong good for file-level

how IT managers approach the SAN vs. NAS decision. While the technology and

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Business Benefits of NAS NAS devices are certainly less expen-

vs. NAS: The Critical Decision

Choosing SAN or NAS Changes to storage technology and networking technology have changed


its capabilities are indeed important to your decision, it is much more germane to carefully examine your business needs and existing infrastructure. inf rastructure. You need to plan for your business needs and processes today, and how and where you might expand in the future. f uture.

As you begin to decide on your storage needs and how to best address those

You could set up both a SAN and NAS devices to complement each other, depending on the feature set you need. It is unique for every organization and every setting. You can use NAS devices to mitigate storage loads in an existing

Fortunately, companies don’t necessarily have to choose between SAN and NAS exclusively. Depending on your needs, you can build out hybrid SAN/NAS storage environment, and offer your users and applications both file-level and block-level protocols. “You have to look at the reality of the environment and what problem you are trying to solve,” says Rose. “If your critical business applications around block level protocols are even 30 percent of your storage load, it

needs, you have to determine where that break even point is within your business, factoringin equipment acquisition and management costs, features and functionality and what is best

network, even if that network already incorporates a SAN. While SANs are extremely scalable, they are still best suited for transaction-intensive operations. NAS devices remain best used for file storage for desktops and workstations. “It’s good to consider four or five options,” says Rose. “Having more information can lead to a more correct decision. You want to make the best use of your existing exist ing infrastructure. You don’t want to have to rip and replace.”

would make sense to go with aa SAN. You canmore use NAS protocols with SAN, but you can’t get block-level storage in a NAS environment. It comes down to what features you need and what you’re trying to accomplish.” It also comes down to the price of the devices, he points out. “If you don’t have $50,000 for a SAN, you’ll have to go with NAS. Your budget is going to define your box, so you have to figure out what that box will be.” The goal is to make business more efficient, to focus on business prob-

suited to solve your business problems.


and how much of an impact that down time would have on revenue generation per employee. The goal then is to design and deploy an infrastructure that will minimize that down time and minimize the impact of lost revenue. “You have to define what solution best fits. There is no ‘Holy Grail’ answer,” says Rose. “Every customer has a

There are clear strengths and best usage cases for both SAN and NAS devices. The best route in determining whether to adopt or expand your usage of SAN or NAS is an individual decision based on your organization’s business processes and storage needs. Gather as much information as possible on your own needs and unique situation and the business problems you are trying to resolve. Then match those needs

lems. Rose describes a formula Dell uses to help its customers figure out what type of solution is going to best fit their business and storage needs. They break down revenue and the percentage of that revenue each employee generates. Then they break down hours per week and overall number of employees. Assuming each employee generates around $10,000 per week, then they calculate the down time within that business when those employees are not able to work,

different problem and there are always different solutions for every problem” As you begin to decide on your storage needs and how to best address those needs, you have to determine where that break even point is within your business, factoring-in equipment acquisition and management costs, features and functionality and what is best suited to solve your business problems. You can consolidate servers configured for block-level storage into a SAN for a less expensive storage solution.

with the capabilities and characteristics offered by a SAN or NAS. And finally, ensure that your selections are within reach of your budget. Only then will you be able to arrive at a solution, or combination of solutions, that will meet your storage and access needs, while fitting within your budget and business processes. As an IT decision-maker, you’re not looking to buy a technology or a piece of hardware. You’re trying to solve a business problem.

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