Ask any group of data management executives what is keeping them awake most nights, and you're likely to hear the same two words ­ data storage. Never before have the demands been greater, technologies more transitory or solutions murkier; and the penalties for choosing the wrong alternative have never been higher.

With storage needs doubling for the average company every eight to twelve months, it is critical that storage networks be scalable and easy to administrate. Yet to this point, there has not been a simple, elegant technology that provides relatively low cost of entry, full interoperability, single-point management, ease of use and the ability to leverage legacy investments in hardware and software both now and as the company grows.

The two dominant storage paradigms available today ­ storage area network (SAN) and network attached storage (NAS) ­ each have significant advantages. SAN, a high-speed sub-network of shared storage devices, has typically been the solution of choice for large-scale, high-performance networks where fast access is critical. The purpose of NAS, by contrast, is to provide highly optimized, integrated storage solutions that can be added directly to a local area network (LAN), usually through a file server and connecting storage devices.

With each technology also carrying its own unique limitations, executives are hard-pressed to find a comprehensive solution that will meet their companies' storage and backup objectives. The good news, however, is that a total, practical solution needn't be a problem. In fact, given new systems and tools now coming on the market, you have a right to demand a suitable remedy.

Technologies are evolving ­ and in some cases are already here ­ that solve the SAN/NAS platform dilemma. Not only can the advantages of each system be applied to the same storage solution, but with these new convergence tools, a highly satisfactory and cost-effective storage network can be created regardless of what storage resources are currently in use.

The Challenges of SAN and NAS

Both SAN and NAS have advantages and disadvantages. SAN was developed with the intent of freeing network resources by disaggregating the storage function from routine network activity. Storage devices are connected via a single, direct connection to the LAN or wide area network (WAN) – typically via Fibre Channel, although Gigabit Ethernet and even SCSI over IP methods are gaining acceptance – accessible by all servers on the network.

By separating storage-area traffic from LAN traffic, efficiencies for both are increased. Users on the network are able to access stored data quickly, and intra-SAN data flow is accomplished without cannibalizing network resources. SAN devices can be separated geographically from most network nodes – as much as 10 kilometers via Fibre Channel connection.

SANs are highly dependable and comparatively easy-to-manage systems that, while expensive to purchase and install, are proving to be cost- effective. Many companies are experiencing a total return on investment within 18-24 months, making the SAN alternative increasingly justifiable for a larger number of companies.

For all the developing advantages of SANs, continuing difficulties are keeping it from being a panacea for storage challenges. At the top of the list is interoperability, especially considering the number and variety of components, protocols and standards present in the usual SAN solution. While industry bodies are working on interoperability issues, it will be some time before they achieve resolution.

Because of the high initial cost and high capacity of SANs, many small-to-mid-sized companies feel that the platform is a bit of overkill for their projected storage requirements. Another fundamental problem is the method of data transmission. SANs communicate at the data block level – the secret to their hyper-fast transfer speeds – while NAS systems communicate at the file level. What this means to SAN users is that file extensions are lost, creating problems for users during data retrieval.

NAS is a relatively recent development designed to provide a less expensive, easy-to-install alternative to SANs. Unlike the SAN configuration where storage hardware is separated from the Ethernet, NAS storage devices reside directly on the network in a distributed arrangement. Each NAS device, a stripped-down server optimized for file management, can be accessed quickly and easily by network users and provides inherent advantages in file sharing and management.

Network Appliance, Inc. and EMC are today's leaders in NAS technology, providing the filer appliances required for NAS installation. One filer is typically paired with each server on the network. Backup is handled by one or more separate backup servers, connected via SCSI hookup to a tape subsystem.

While NAS is a highly practical and popular solution for data storage in smaller networks, its very advantages prove to be its Achilles' heel. The NAS file- level transmission protocol means data backup is slow – a major problem in networks that are busy 24 hours a day, such as Internet service providers (ISPs) or WANs. User requests for data, as well as tape-backup sequences, often stress LAN resources and can significantly hamper network performance.

Several solutions are being considered to lessen this problem. One is to attach a tape subsystem directly to each filer using SCSI cabling, an expensive alternative that also results in additional administrative duties for managing multiple backup sequences. Another option is Gigabit Ethernet, which will surely improve performance as the technology becomes widely available.

NAS solutions, whatever their configuration, present management problems for IT staff due to the wide physical deployment of storage and backup devices. Not only is routine maintenance and supervision complicated, but because the devices are installed near their assigned servers, disaster protection is lost.

A Unified Solution

In reviewing the plusses and minuses of SAN and NAS, it becomes obvious that a better solution is needed, one that removes the interoperability and hardware issues and improves overall system performance.

A consortium of leading storage technology companies, including Network Appliance, StorageTek and BakBone Software, has offered a fresh solution to the problem of efficient LAN data backup. The group is suggesting a SAN/NAS hybrid employing a SAN tape subsystem, jointly connected to multiple NAS filers using Fibre Channel cabling. The subsystem, routed through a Fibre Channel host bus adapter and controlled by a switch, enables high-speed backups to take place directly from the filers without disrupting LAN traffic.

By employing both filers and SAN connections, the system enables files to be shared in their native format, yet can be backed up using the data blocks employed in a classic SAN solution. The platform enables tape devices to be centrally located, easing maintenance duties and providing adequate disaster recovery protection.

Certainly this cross-platform effort is worthy of consideration for those companies that have made the decision to upgrade or replace their current storage networks. However, with today's advanced technology, it shouldn't matter what system resources are currently being used. Whether SAN or NAS, the solutions are available to make data management seamless, scalable, fast and easy to administrate.

Software solutions now exist that provide scalable, truly modular storage management using legacy resources. Addressing interoperability and distributed deployment issues, these solutions operate in multivendor networks, supporting a broad range of servers, clients, database applications, storage media and high-performance storage devices from single drives to multiterabyte libraries.

These data management solutions speed bi-directional data transmission by bypassing the backup server. Data travels directly from the storage disk source to the client owning the data, then on to the tape drive via the most efficient network path. The backup works in both SAN- and NAS- centric environments. In SANs, the data is delivered directly from servers and clients to tape drives across the SAN platform, while NAS solutions benefit from tape library sharing via SCSI direct connection to the tape drives, bypassing slow networks and greatly reducing the backup window.

Quality storage management software can scale from individual user to workgroup to enterprise without sacrificing performance. Administration for the entire network is provided via a single, easy-to-use GUI; and all network management is accomplished within the core code – no need for additional layers of complex and costly software.

The Move Toward Virtualization

Companies using modern data management software can perceive network storage resources as "one big disk." This improvement in system administration is the cornerstone for storage virtualization. With storage virtualization, the line between local and network storage resources is blurred, enabling users to save files with no regard to their actual physical location.

The ease-of-use implications of this advancement are obvious. From the user's point of view, all he or she knows is that there is one huge storage disk on the network. Meanwhile, the enterprise is able to optimize storage resources LAN-wide, whether on workstations, servers or backup devices.

Because no virtualization standard currently exists, individual vendors are pursuing their own configurations and standards that emphasize various user benefits. Some are pushing system performance, for example, while others concentrate on ease of use and maintenance. As the market matures, however, a single scheme will undoubtedly be adopted.

Despite the fact that standardized virtualization is not yet here, it's obvious that sufficient technology is already on the market to effectively bring together the diverse hardware, network architecture and other legacy resources present in the typical LAN. With the right software driving the system, any company's storage solution can become scalable, easily controlled, cost-effective and totally integrated using existing network elements.

Data management professionals and IT administrators should take the time to investigate these alternatives before making their storage management investments. It's a sure bet they'll sleep better for it.

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