The next major development in network integration is Storage Area Networking (SAN), but what does this mean for you and how well prepared is your business to reap the bountiful rewards it would seem to promise? Geoff Marshall looks at the new technology, sans which network administrators could be that little bit poorer

In the past year the storage industry has witnessed some serious shake-ups with SAN — Storage Area Networking —being hailed as the next big thing. There seems to be plenty of hype associated with all of this, but when you get down to basics storage, in any capacity, has become imperative to a company’s success. Independent research company IDC, in November 98, identified that 47 per cent of the price of a company’s computer systems was storage. Such a large percentage means that there are huge opportunities in selling storage solutions.

SAN is the latest storage technology and, despite the plethora of superlatives, there are many benefits to it. Vendors like EMC seem to be driving SANs but in reality they have a very proprietary solution that works mainly across mainframes. CLARiiON, on the other hand, are fervent believers in open SANs that are scalable and standardised, allowing companies to invest properly in SANs over time and according to their needs, as opposed to paying one huge sum up front.

If SANs are to become truly open then a standard is needed, with commitment from all the vendors such as Legato, VERITAS, Sun, etc. If no standard is found this will only lead to a series of disparate and unconnected solutions, where users can only suffer in the end by becoming locked up into one vendor's solutions.

What is a SAN?
The Storage Network Industry Association defines storage networking as involving networks whose primary purpose is the interconnection of storage elements, with connections to other systems (such as servers). The difficulty inherent in a SAN is overcoming the limitations of the architectures typically used to connect servers to storage systems to implement a more open ‘any-to-any’ network. A true SAN is enterprise-wide, incorporating heterogeneous storage and networking equipment. The SAN is typically deployed to: implement high-availability disaster protection; to ensure server and storage resilience; and to speed up backup and archive activities.Backup operations should be able to take place alongside normal applications, without impacting network or server performance. SAN centralises and consolidates storage, for storage equipment is an expensive resource and must be used efficiently.Following 3Com’s decision to quit the SAN market, StorageTek’s package of job cuts and HP’s move to divorce itself from EMC you could be forgiven if you had doubts about how best to implement an enterprise-wide data storage solution that truly meets your needs.

And with all the media hype surrounding the ‘new’ storage technologies of Network Attached Storage and Storage Area Networks, it may be just the time to consider the future of the storage medium — regardless of the network type used!

Bypassing the server
Storage systems are frequently accessed via a server, using tools such as FTP or NFS, imposing a heavy processing overhead on the server. A SAN can free up the server from such tasks (eg, for data backup operations), leaving it to perform its primary function. With the availability of ATM and other technology multi-gigabit enterprise networks are being deployed, offering the bandwidth and QoS guarantees needed for storage networking without impacting other traffic. I spoke to Andrew Rowney, sales and marketing director of Storage Area Networks Ltd.

The only network technology able to deliver cost-effective, scalable, guaranteed high bandwidth links in the wide area is ATM," he comments. "Storage Area Networks Ltd has developed DiskLink, a SCSI/ATM switch that allows organisations to integrate storage traffic with existing enterprise-wide ATM networks. If you are familiar with ATM edge products such as Sphere, CellStack, FVC and PictureTel, you will recognise DiskLink as the ATM edge product for storage networking. "

DiskLink is a high-performance storage area networking device that delivers unlimited SCSI extension over the new generation of cost-effective ATM wide area links."

By transferring data at the SCSI command level DiskLink avoids the costly and time-consuming server overheads and protocol conversion delay normally required with wide area links," claims Rowney. "DiskLink allows storage traffic to be multiplexed with other services, such as voice, video and LAN traffic on the existing corporate ATM network, thus reducing MAN/WAN costs and complexity."

A virtual SAN can be created using guaranteed ATM bandwidth. DiskLink employs sophisticated ATM traffic-shaping techniques to make cost-effective use of limited wide area bandwidth. Storage Area Networks Ltd also has a forthcoming Fibre Channel/ATM device."

IBM has advanced its Storage Area Network (SAN) initiative with new SAN-ready server and storage technology, software and services to help enterprises of all sizes to manage, build, access and store business-critical information centrally. By the year 2002, IBM estimates that 70 per cent of all medium- and large-sized customers will implement SANs to manage and share the volumes of data created as they transform themselves into e-businesses."

Information is the currency of an e-business and must be managed as a valuable corporate asset," says Dr James T. Vanderslice, senior vice president and group executive, IBM Technology Group. "SANs are the digital bank for that information. This makes SANs one of the most important IT advancements since the emergence of network computing. "IBM is committed to be the industry’s premier total SAN solutions provider," Vanderslice adds. "No other company can bring together a combination of storage, services, and servers and software to take advantage of this important trend."

Regarding SANs, Mike Harper, marketing manager for StorageTek’s Network Systems Group, comments: "One of the most important arguments for implementing a SAN is the common centralised use of storage systems by all servers and the resulting increased availability of the complete storage environment. Storage management intelligence can be embedded in the server, storage controller or network. Server-embedded implies that storage is accessed through the server. The central issue here is that the storage becomes captive to the server. The data movement from the server is handled through the server operating system, which has limited data bandwidth and access facilities that limit sharing of storage devices. When storage is embedded in the storage controller device itself, data movement is limited by the bandwidth of the I/O link to the storage device."

Depending on how clients are connected there may also be dependencies on the server operating system to execute data movement between the client and the storage device.

Network Appliance points to the shortcomings of SAN in the areas of data to desktop, heterogeneous data sharing and lack of standards for file access and locking. Network Appliance has combined the benefits of SAN and NAS (Network-Attached Storage) to produce what it describes as a complete solution that gets away from such shortcomings. According to Steve Ronksley, managing director of UK Network Appliance: "We have developed the notion that, by combining NAS and SAN, we can reduce the shortcomings the applications have individually and integrate the benefits."

When separating the data from the application, Network Appliance reduces any unnecessary complexity with a complete network storage solution. We have found that, by combining the benefits of SAN and NAS architectures, we can create a powerful storage solution for even the most complex data centre requirements."

Optical storage
According to Ringdale, the dominant storage medium for the foreseeable future is almost certainly going be ‘disc shaped’ and have a hole in the middle! Optical storage (CD, MO or DVD), therefore, is increasingly becoming the preferred option as it offers enormous advantages over other secondary storage devices such as tape, microfiche and paper. The challenge is storing, handling and managing the disks used for data storage automatically and efficiently. Since the advent of the CD, some vendors (JVC, Plasmon, Ringdale, Sony) have produced different solutions using optical media. Ringdale can supply a turnkey-system called Optica Storage Server, which is a highly scalable network data storage system that is ideal for many application areas, including NAS and SAN infrastructures. The system’s modular design utilises the industry-standard 19-inch rack cabinet and can accommodate up to 1,200 CDs per rack, a mix of CD ROM, MO and DVD drives, a built-in server and an optional uninterruptible power supply (UPS). If required, additional racks can be added to provide storage of 100,000 CDs or more.

Regarding standards and compatibility Chris Boorman from VERITAS made the following observations: "SANs are in the early phase of implementation. It is difficult to find reliability and interoperability of hardware. The compatibility issue is getting better. VERITAS is providing certification testing for software with different types of hardware to improve this situation. People think that backup is the first obvious benefit of using a SAN. However this is not strong enough on its own. Clustering is a far stronger reason for using SAN, and back-up for clustering enhances the basic availability of the application.

"Regarding standards, as the market is growing so quickly the problem is for standards to keep pace. Basically, software and the benefits it could deliver, is ahead of hardware; without hardware in place, VERITAS and other software companies are restricted in the ways they can manage and control the manner in which data is being moved and controlled."

Other companies that are now active in the SAN market include MetaStor (which is a brand name of LSI Logic Storage Systems), Legato Systems and Gadzoox.

Organisations considering implementing storage area networks will be sophisticated IT users. Their current storage systems will almost certainly be SCSI-based. The major applications driving storage area networks are on-line mirroring to disaster recovery sites, and off-site backups requiring access to remote systems over distances beyond the reach of local area networks or extender technology.

For efficient implementation, wherever possible the storage area network will utilise the enterprise network and remove data traffic from the network servers. Storage area networking is a relatively new phenomenon, currently enjoying much attention. But before deploying the technology make sure that you have a clear understanding of application requirements, existing storage and network infrastructure, and consider these against the issues we’ve outlined above.

Above : Legato Networker provides storage management and data protection across a network

Above : products from CLARiiON’s family of full fibre channel-based
SAN solutions

The F760 solo filer from
Network Appliance

Chris Boorman of VERITAS: the compatibility issue is getting better