Advancing New Enterprise storage beyond the campus.

In the age of the New Enterprise, everything happens in Internet time, and staying competitive has never been more challenging. Perhaps the greatest challenge lies in dealing with the storage demands of today's businesses. Not only does stored data have to be accessible at all times and from anywhere within the enterprise, but the demand for lowered costs to store ever-increasing amounts of online data is accelerating.

In 1995, experts estimated that the total storage capacity of the world's computers was approximately 200 terabytes. In just over five years, that storage capacity has grown 500,000-fold to nearly ten exabytes. With this dramatic increase in data being stored online, it seems unlikely that any single storage topology--whether direct-attached (DAS) or network-attached (NAS) storage or a storage area network (SAN)--can provide both the speed and reliability of access while, at the same time, providing the most cost-effective solution for the diverse suites of applications being run in today's global enterprises. So while battles rage over the best storage topology--SAN or NAS or DAS--innovators like Storage Computer have been designing new architectures that incorporate the strengths of each of these topologies and create an entirely new category of networked storage--Storage Wide Area Networking (SWAN).

Defining Storage Topologies

Many storage topologies have emerged over the years as storage has taken on an increasingly important role. Analysts like Anne Skamarock of Enterprise Management Associates now predict that within three years large companies will spend three times as much on storage as they will on computer hardware. Given that, it is hardly surprising that there are so many incumbent and emerging storage topologies seeking to solve the problem. What are the choices?

Direct-Attached Storage Dominates

Direct-attached storage (DAS) is certainly the most familiar, and it is ubiquitous. For decades, computer storage devices have been directly attached to the host computing platforms, which generate the data being stored. PCs and servers come bundled with direct-attached storage when they are purchased. And there are distinct advantages to the DAS topology: high performance without any network latency or bottlenecks to contend with. But in today's business climate of shared information and resources, the disadvantages of non-networked storage are beginning to outweigh the DAS advantages, particularly as latency and bandwidth issues associated with other topologies are being resolved.

Network-Attached Storage Emerges

Network-attached storage (NAS) is becoming more popular as network bottlenecks are minimized with increasingly higher speed protocols and higher bandwidth media. NAS promises to be a very efficient and cost-effective means for consolidating storage on a network and sharing fries among users on multiple diverse host platforms. Using the same Ethernet network currently used for local-area communications to transport storage data can bring cost efficiencies. And, at the same time, it can simplify and consolidate management of storage and network traffic within a single infrastructure. Although NAS is well suited to handling file-oriented applications, data-intensive, transaction-oriented applications may be better" suited to Fibre Channel-based SAN solutions.

Storage Area Networks Are The "Hot" Storage Topic

While NAS devices connect directly to the Ethernet network and transport files across that network, SANs move blocks of data between host servers and storage devices through a Fibre Channel switch. Storage Area Networks (SANs) are creating a great deal of industry "buzz" these days, particularly those that tout storage virtualization techniques. The storage devices reside on a dedicated storage network, so that the production data network is not overburdened with added storage traffic. SANs also make more efficient use of physical storage devices by "pooling" available physical resources on a dedicated, Fibre Channel-based storage network and allocating the storage among multiple host processors using the SAN.

Choosing The Right Solution

Choosing the right solution is not always easy, for each of the storage topologies that we have discussed have limitations and disadvantages to offset their advantages. While DAS dominates today and offers optimal performance for local users of the storage system, it is limited in its ability to support the shared data and shared resource requirements of many New Enterprise applications. The economies of scale and cost efficiencies of shared resources offered by both NAS and SAN are missing in DAS topologies. Even the best and most sophisticated RAID solutions and high-end disk arrays cannot offer the same efficient utilization of the physical storage area that is available in SANs. Nor can they offer the file sharing capabilities and the consolidated management of storage and data traffic using the same infrastructure that characterizes NAS solutions. But DAS is not going away just yet, just transforming. DAS still offers outstanding performance and is cost-effective in many instances. And although NAS offers many benefits, it is not the perfect solution in terms of scalability or performance. Some of the benefits of NAS include:

* File sharing by heterogeneous hosts

* Use of existing network infrastructure

* File access performance improvements

* Simplified configurations

* Faster installation

* Ease of integration into the existing infrastructure

* Improved automation of backup and recovery

The drawbacks of NAS include added protocol overhead and latency, network bottlenecking, and limited capability to scale without performance degradation.

SAN solutions, particularly those offering SAN virtualization software, promise to resolve the issues of latency and bottlenecking and to offer "virtually" limitless scalability. Today's SANs pool all available storage resources on a dedicated, Fibre Channel-based storage network so that portions of this "storage pool" can be allocated among the host processors using the SAN. Several benefits are derived from SANs, including:

* Easy storage expansion with reduced downtime 

* Improved performance through a dedicated storage network

* Non-disruptive, LAN-free backups

* SANs eliminate the need for host processors to manage physical storage

* Combined heterogeneous storage represented as a single, centrally managed storage pool

* Single, consistent storage interface and management model

* Minimization of backup windows and reduced data recovery times

* Increased uptime and reliability

But SAN solutions are still relatively expensive to implement and complex to install and configure. Further, Fibre Channel SANs are still plagued by vendor interoperability issues. The other issue plaguing current SAN implementations is that Fibre Channel is a serial interconnect between host and storage device, not a network. As SAN technology evolves, an IP-based transport standard will be needed to bring SANs into the Storage Wide Area Network, which represents the future of New Enterprise storage.

Which Topology_ Should Be Used For Which Applications?

Despite all the hype about various new higher-speed connectivity options and protocols, the element most critical to the delivery of storage performance is the storage device itself--and the sophistication of its hardware and software. Everything needed to get data to and from a logical device occurs at the storage subsystem level. And the network--whether a dedicated storage network or a combined communications and storage network--will either aid or hinder storage subsystem performance depending on the configuration. Under most current industry thinking, the profiles for major network deployment options have been described as follows:

Storage area networks

* For transactional, highly available database data

* For large blocks of data

* For data warehousing; enterprise resource planning applications

* Requires familiarity with Fibre Channel

* Requires knowledge of storage management techniques

Network-attached Storage

* For front-office applications

* For handling files

* Requires familiarity with Ethernet

IP Storage--Foundation of SWAN

* For both handling blocks of data and files

* Familiarity with Ethernet and IP

* For Enterprises and Front office applications

There is clearly a role for each of the networked storage options described here, as well as for other storage topologies, which have yet to be defined. What is important to New Enterprise users is that the solutions they choose today are based upon an extensible architecture designed to accommodate changes brought about by market and technology evolution.

Defining the Solution--The Storage Wide Area Network

SWAN, or Storage Wide-Area Networking, identifies the next logical evolutionary step in networked implementations. There are many benefits to integrating storage and data networks to achieve economies of scale, as well as simplified consolidated management. But there are issues that need to be resolved before such integration is feasible. Storage is supported by SCSI and Fibre Channel protocols and is tied to physical, mechanical devices that require high speed throughput. WANs are based on the Internet Protocol (IP), which is asynchronous by nature. IP networks can operate with far fewer restrictions than storage networks. Distance limitations are a major factor in storage networks, while 1P networks know no distance limitations. The advent of gigabit Ethernet and optical networking is transforming the issues related to IP networks. Through increased optical speeds, advanced Quality of Service options, and reduced switching, overhead bottlenecks and latency storage applications can now prevail in the IP world.

Why SWANs?

A SWAN deployment is the natural evolution and convergence of the industry's accepted storage topologies including Direct Attached Storage (DAS), Storage Area Networks (SAN), and Network Attached Storage (NAS). What enterprises are looking for as the storage market evolves are technologies that effectively marry the speed and performance associated with DAS, and the management simplicity as well as the ability to share data repositories among multiple file formats found in NAS deployments. SANs have been seen as the potential answer, but expense, vendor interoperability issues, and difficulties associated with implementation and maintenance have limited widespread SAN adoption. However, a properly deployed SWAN offers exceptional ease of network facilitation and management, deployment of remote data archiving and replication, high speed data access anytime, anywhere, and a significantly lower total cost of ownership.

Todd Viegut is the vice president of marketing at Storage Computer (Nashua, NH).

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