The demand for storage capacity continues to surge today, fueled by the growth of the Internet and a rising demand for online access to data. The ability to move and access data has become a mission-critical capability for every enterprise, and there is great pressure both to improve data management and reduce total cost of ownership (TCO). The industry is responding with storage networking technology that will add three significant capabilities to corporate network architectures. First, companies will be able to architect shared storage pools that can scale seamlessly. Second, they will be able to greatly reduce restore and backup times by leveraging online archives and new types of secondary storage media. Third, they will enjoy far greater manageability of data because they will have control of their databases from a single central point. The combination of these three things ­ scalability, much faster recovery and backup, and manageability ­ will inevitably reduce TCO of data storage in the near future.

These benefits make a revolution in data storage inevitable ­ in fact, it is well underway. Storage networking, whether network attached storage (NAS) or storage area network (SAN), has become essential to mission-critical IT environments. It is the dominant trend in data storage. Gartner estimates that end-user expenditures on storage networking solutions will exceed $65 billion in 2003. For database managers, the burning question now is: How can we get the greatest return from a major investment in storage network architecture?

This brings us to the debate about the relative value of NAS and SAN technologies. A NAS system is essentially a plug-and-play storage solution based on industry- standard networking architecture and attached to a local, metropolitan or wide area network. Its inherent design eliminates server I/O bottlenecks on heterogeneous networks by providing cost-effective storage and file sharing. On the other hand, we can describe a SAN as the vision of an open, scalable, fibre channel architecture that interconnects storage systems, backup devices and servers. It absorbs LAN traffic to improve network performance. Figure 1 highlights the prime differentiator between NAS and SAN technology.

In NAS, a single central file system resides in the architecture of the NAS appliance and controls data storage. In a SAN, the file systems are part of the operating systems that reside on multiple servers. The existence of multiple servers implies that data must be stored in a variety of file systems and formats, which makes true data sharing a challenge. NAS appliances, on the other hand, communicate with different operating systems environments (e.g., UNIX and NT) to achieve true single-copy data sharing.

Figure 1 also explains why NAS is a reality today and SANs remain a vision. NAS, which is based on standard protocols, connects to the LAN, based on reliable standards developed over the last 15 years. On the SAN side, the interoperability technology between different servers and storage units remains largely undefined as the standards and protocols are still being developed.


Figure 1: Prime Differentiator Between NAS and SAN Technology

However, both NAS and SAN solutions offer significant performance advantages over traditional server- attached storage in a networking environment. Some see them as competing, mutually exclusive or orthogonal; but it has already been pointed out in this article that SAN and NAS are complementary, interoperable and that each has its place in corporate network architectures. The view that they are orthogonal is outmoded. To understand where they're going, we have to examine another trend in storage networking technology: convergence.

Destined to Converge

It is now clear that the distinctions between NAS and SANs will ultimately bring them together as parts of a single solution. NAS and SANs, like all networking technologies, have architectures that include challenges, although NAS technology is clearly meeting important customer needs. Here are some of the issues affecting NAS and SANs:

  • NAS is not perceived as being as scalable as SANs, although it can be readily scaled by adding capacity up to multiple terabytes or by adding multiple NAS appliances on the network.
  • There is a lack of fully functional fibre channel SANs because interoperability standards remain undefined. In the meantime, gigabit Ether-net (GbE) SANs have been introduced to provide a more standardized approach to SAN architecture.
  • The industry faces the challenges of incorporating SANs into a coherent strategy that leverages the huge infrastructure based on networking technology by industry leaders such as Cisco Systems, Foundry Networks, VERITAS and Legato Systems. A related problem is that personnel must be trained and available to support these new systems without exacerbating the staff shortages plaguing IT today.

Where does this leave companies that need to improve the TCO of their business solutions, including their IP infrastructures, and are in search of the ideal storage networking solution? They will drive the convergence of NAS and SANs for these reasons:

  • Customers deeply committed to both NAS and SANs recognize that some of the powerful features they want are available only in NAS and others only in SANs. Therefore, they will be looking for best-of-breed solutions that deliver the best of NAS and SANs ­ but without their limitations. Market pressure will move the industry to accommodate these customers.
  • Companies want at least a five-year return on their technology investments, and they are very much in the driver's seat today. They want to leverage their existing infrastructure investments, including human resources, applications software, compute servers and networking infrastructures. Convergence means a longer useful life for storage networking technologies.
  • Companies can't afford to stop doing business while they deploy an entirely new infrastructure. They will want their NAS and SAN implementations to merge and reinforce each other.

Trends in networking technology also support the concept of NAS/SAN convergence. Technologies are beginning to borrow from each other fairly heavily. Ethernet achieved gigabit speeds by leveraging gigabit fibre channel. When fibre channel reaches 10GB speeds, it will do so by leveraging the work that led to 10GB Ethernet. We can expect this kind of convergence to apply to the different types of physical media used today for storage networking, whether they involve storage-oriented protocols or network-oriented protocols. They will ultimately merge into a single physical infrastructure from a networking standpoint.
Another significant technology trend that favors NAS/SAN convergence is the rapid rise in networking speed as depicted in Figure 2. Network speeds are now surpassing storage speeds, blurring the lines between NAS and SANs from the standpoint of underlying technology. Customers will soon begin to focus more on the value proposition of storage networks and worry less about GbE versus fibre channel architectures.

InfiniBand exemplifies the way technology is helping to drive this convergence. Infiniband is being designed to take advantage of well-established existing media such as the enormous dark fiber networks already in place. It's already clear to the companies driving the InfiniBand standard that InfiniBand must be congruent with NAS/SAN convergence. InfiniBand is being designed to accommodate it ­ which, in turn, is helping to drive the convergence.

Finally, a recent industry development that favors convergence is the open standards initiative of direct access file system (DAFS) by a consortium of companies (see www.dafscollaborative.org). DAFS is a file system protocol based on virtual interface (VI) standards that has been fostered by Intel in recent years. DAFS eliminates storage I/O latencies by using direct memory access (DMA) operations between servers and storage memory architectures. DAFS will blur the lines between NAS and SANs even further because it is aimed primarily at the storage network environment and is agnostic to GbE or fibre channel mediums.

The storage networking technology built around this convergence trend will contain both NAS and SAN technologies in the same product. Any other approach would be less than optimal because companies are not likely to buy two products when one will do. Picture this solution as an intelligent box. On one side are storage technologies and storage protocols to manage disk systems. On the other side are network-oriented protocols for delivering the data from storage to the outside world, including database servers. These same network protocols are used to provide high-speed access to a common automated tape library. This is true cost-effective NAS/SAN convergence, and it exists today.

OSN: Catalyst for Convergence

The most powerful force driving NAS/SAN convergence, however, is open storage networking (OSN). OSN is based on the concept that linking pools of storage with networking technologies is essential to giving companies the data they need whenever they want it, with perfect data integrity. It is our conviction, based on considerable experience, that companies will soon be making it an absolute requirement that these integrated NAS/SAN solutions be delivered as open industry standard solutions. The OSN design concept allows companies to construct best-of-breed data access and management solutions that readily integrate legacy equipment, as well as new and emerging storage and networking technologies. By implementing solutions that are truly open, companies fully leverage existing management tools, staff, knowledge and equipment resources while benefitting from the best offerings of a large, mature and diverse base of suppliers. Organizations can focus on their business problems and opportunities ­ not on evaluating, testing and integrating new technologies.

The storage network of the future will be based on open standards ­ open protocols, open hardware technologies and open software technologies ­ that are plug-and-play interoperable and can be combined to match the customers' needs. The breathtaking ascent of far faster networking technology and rising volumes of data demand it. Networking technology is expected to unify the LAN/MAN/WAN environments by 2003. By focusing so clearly on leveraging existing networking technology, OSN delivers reliable, affordable access to any type of data anywhere, anytime.


Figure 2: Rapid Rise of Networking Speed with NAS/SAN Convergence

This open architecture facilitates the convergence of NAS and SANs. Customers will be able to adapt storage resources to drive applications to greater levels of scalability, performance and data availability. Data availability, in fact, may well be the critical issue that moves many companies to adopt best-of-breed solutions that include NAS and SANs in an OSN environment. InfiniBand will also drive NAS/SAN convergence and the adoption of OSN. It will be adapted to OSN and enthusiastically embraced by customers.

The industry is now using OSN to enhance the connectivity layer of SANs and combine them with the power of NAS to deliver an improved storage-over-a-network business solution. The solution architecture spans both NAS and SAN hardware and software technology, and incorporates a powerful data management capability to eliminate the shortcomings of both SANs and NAS. The result is mature SAN management functionality, leveraging existing standards such as simple network management protocol (SNMP). The solution, which is commercially available today, uses OSN as the only acceptable standard to integrate best-of-breed multivendor technologies that dramatically reduce TCO and protect customer investment.

To Sum Up

NAS and SANs are complementary technologies. They are converging today under the pressure of powerful market and technology trends. OSN is the ultimate force that drives the convergence and permits standards-based, best-of-breed solutions.

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