Storage-Area Networks

As public information pours into state and local agency networks via the Internet, government data volumes are swelling beyond the capacity of existing networks and servers.

To help solve the problem, state and local agencies are turning to storage-area networks to safeguard their mission-critical information. SANs store data in separate, dedicated networks, where data can be centrally managed, administered and backed up. Data is separated from applications, but users can access data from the desktop as if it were on their hard drives.

SANs have been around since 1991, when IBM Corp. introduced Escon-Enterprise Systems Connection-a fiber-optic channel that transfers storage data at 10 megabits/sec up to 5.6 miles between systems. Within the confines of the proprietary Escon, any network device could interoperate with any system, creating a secure, highly flexible "any-to-any" storage environment for mission-critical data.

Although limited by a lack of interoperability, today's open, or heterogeneous, SANs offer similar benefits in the client/server environment. "SANs allow you to host mission-critical data at the required availability level on distributed networks," said Michael Peterson, president of Strategic Research Corp., Santa Barbara, Calif., and former president of the Storage Networking Industry Association (SNIA).

There are four forms of SAN connectivity used today: Escon, Fibre Channel, SCSI and Serial Storage Architecture. Fibre Channel, the actual physical cable, is considered a default connectivity standard for SANs. But vendors have implemented different versions of the Fibre Channel protocol, and dissimilar storage and network devices run on them. Plus, there are no application programming interfaces (APIs) that permit storage-management software packages to communicate with one another.

SAN vendors are working on standards that will alleviate the interoperability barriers limiting heterogeneous SANs. "We're doing three important things with SNIA," said Scott Drummond, a senior marketing manger for IBM Storage Systems Division, San Jose, Calif. "We're working on Fibre Channel protocol standardization, on the [Management Information Block] definition between storage devices and on APIs so storage management software packages can talk to each other." IBM is a founding member of SNIA.

State of Washington

Washington didn't wait for ideal, standard SANs to be realized before it took advantage of their technological benefits. Using EMC Corp.'s Symmetrix Enterprise storage systems, the state's Computer Services Division houses 3 terabytes of data that covers all departments in the state except the Transportation Department.

The four EMC storage systems are cabled into IBM 390 mainframes with fiber. Applications run on the mainframe, and storage is housed separately in the Symmetrix systems. The mainframe is attached to the network, and the EMC systems are attached to the mainframe.

However, for mainframe applications to get to storage that is located on a Unix or Microsoft Corp. Windows NT system, the division has to move the data using an established utility, such as File Transfer Protocol, Open Database Connectivity or Logical Unit, an IBM mainframe system. The lack of interoperability is one of the issues SNIA is addressing.

"The real issue is the technical ability of 'any to any,' " said Michael McVicker, assistant director of Washington's Computer Services Division. "The problem the

SAN is trying to solve is to establish one standard data-access architecture, one common interface, and put all the data on the network behind it so any machine can get to that data using that one interface.

"Today, it's all different interfaces, one interface from the [IBM] 390 to [Windows] NT and another interface from Unix to [Windows] NT. Today, we've got lots of one-to-ones but no any-to-any," McVicker said.

Top SAN Benefits

The primary benefit of a SAN, McVicker said, is the separation of data from applications, which can be spread out all over the network, while the data is centrally administered in the SAN.

Washington state has been able to achieve most, if not all, of these benefits. For example, while McVicker does not have "any-to-any" capability and does not share storage between disparate systems, he does have separate storage and applications, scalability, centralized management, continuous access and fault tolerance.

Users and vendors agree that the ideal SAN should be open. "The marketplace is heading in the direction of heterogeneous, any-to-any connectivity," said Doug Fierro, manager of network solutions for EMC, Hopkinton, Mass. "But it's another thing to give customers the insight and manageability of the connection."

As a means to that end, EMC has been working with SNIA on the MIB, or Management Information Block, definition between storage devices, which was recently accepted by the Internet Engineering Task Force (IETF), an Internet standards group.

City of Toronto

Toronto has implemented a SAN, not just for its storage benefits but as part of a Year 2000 solution. Working with Storage Technology Corp., a Louisville, Colo.-based mainframe storage company now focused on SANs, the city implemented a 4-terabyte SAN that services 10 systems.

StorageTek provided most of the pieces needed to build the SAN, including Fibre Channel, access hubs, disk subsystems, maintenance and professional services for project management and implementation. Veritas Software Corp., Mountain View, Calif., provided the storage management software.

Just as Toronto grew from seven boroughs into one large city-now the fifth largest in North America-Toronto's Computer Operations Division has consolidated 1,100 servers across seven data centers into one large data center that has 500 servers. The new center will house a mix of AIX, Sun Microsystems Inc. Solaris, Intel Corp., Microsoft Corp. Windows NT, Novell Inc. NetWare and IBM mainframes.

"We knew the nightmare of dealing with local storage on each system and disk subsystems attached to servers that you couldn't share," said Lana Viinamae, director of computer operations and Year 2000 for Toronto. "The SAN has provided us with a lot of flexibility so we can use the storage regardless of what we do with applications."

When Viinamae recognized what she would have to do to accommodate the city's amalgamation of systems as well as the Year 2000 problem, she decided to store mission-critical data in a separate, scalable, fault-tolerant network-a SAN.

As a simple first step to mitigate the risk of making such a big change, Viinamae chose to use StorageTek's access hub to make physical, rather than logical, changes in connectivity.

"With the hub I can connect any server into any disk subsystem, but I make the change physically," she said. "But we're going to a StorageTek switched solution, so we will be able to link any server to any piece of storage on the network." However, like most SAN users today, she still does not have total any-to-any connectivity.

Toronto is using Fibre Channel, which analysts cite as the de facto standard form of SAN connectivity.

"It's wrong to say we don't have connectivity standards. Fibre Channel is a standard," said Nick Allen, vice president and research director of storage for the Gartner Group. "What we don't have is SAN management standards."

Allen pointed out that two of the most important standards under development are Internet Protocol over Fibre Channel and SCSI over Fibre Channel. But SNIA isn't moving fast enough, he said. "We're in the early days of local-areas networks with SANs."

Other industry observers see a similarity between the development of LANs and SANs as well. "We're at the stage of development where LANs were in the mid-'80s when people were building small to midsize LANs," said Scott McIntyre, business line manager of Storage Networking Legato Systems Inc., Palo Alto, Calif.

However, McIntyre pointed out that SANs are not like Ethernet LANs, for which users could take any hub or switch off the shelf and expect it to work with any other hub or switch. In the SAN environment, that situation is a goal, not a reality.

"In SAN environments, one of the great promises is to share resources among multiple disparate servers and applications. Fibre Channel gives you the connectivity to connect tape libraries to multiple servers. But you still have to manage that to make sure two servers aren't trying to write data to the same tape at the same time," McIntyre said.

Legato offers traffic cop software, called Media Management, which allows multiple servers and applications to share tape libraries. The software is based on the IETF-accepted version of the MIB that was agreed upon by SNIA. This early version is part of the Simple Network Management Protocol being developed for Fibre Channel. SNMP is an established network management standard.

"We've made progress in the last six months," said McIntyre, who is on SNIA's board. The standards group recently developed a proposed standard for a copy command that moves data from one device to another without having to move data through a server or a LAN.

"This is a step in the direction of any-to-any and direct device-to-device data movement," he said. "We'll have intelligent devices talking to each other vs. dumb devices, which hang off a server with all the intelligence in the server."

McIntyre and others in the SAN market have high hopes and see great promise for this technology. "We're just beginning a long voyage to see what networking is really going to mean to storage," Gartner's Allen said.

Cheryl Gerber is a free-lance writer based in Kingston, N.Y.


SAN Technology Goals

1. Any-to-any (device or system) connectivity.

2. Sharing of storage resources among systems (desktop, Unix, Windows NT, mainframes).

3. Separation of storage traffic from application traffic.

4. Independent scalability of storage resources.

5. Centralized management and administration.

6. Continuous access and fault tolerance.

Source: Strategic Research Corp., Santa Barbara, Calif.


Revenue Growth of the Storage-Area Network Market


Hardware/$3.3 billion/$13.4 billion

Software/0.6 billion/2.2 billion

Service/1.7 billion/6.7 billion

Total/$5.6 billion/$22.3 billion


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