SANs rise on fed horizon
- By Cheryl Gerber
- May 09, 1999
Faced with the prolific growth of data and networks, a growing number of federal users are building early versions of storage-area networks on which they can offload traffic from increasingly burdened local-area networks.
An extension of a client/server architecture, SANs are used to centralize storage systems. They usually are based on high-bandwidth, proprietary Fibre Channel cable and are composed of Redundant Array of Independent Disks (RAID) controllers, disk drives, network switches or hubs, and host adapters. The goal is to provide fast enough access to centralized storage so that users do not need to maintain their own storage systems locally.
But most agencies will be unable to install true SANs until a newly formed group releases standards to address incompatibilities among SAN products. Last month, a large group of computer and storage vendors established the Storage Networking Industry Association to create open SAN standards that would eliminate hurdles that prevent file sharing and networking in SANs today.
The lack of standards has forced agencies to improvise with ad hoc SANs that may evolve into the real thing as standards mature. "You can't run [Transmission Control Protocol/Internet Protocol] on Fibre Channel yet, so people are using their existing standard networking topologies, such as Ethernet, [Fiber Distributed Data Interface] or Token Ring," said Page Tagizad, director of product management at Procom Technology Inc. "But if they are doing that, then it's not a SAN. A true SAN runs Fibre Channel."
Fibre Channel increases storage capacity far beyond traditional SCSI architectures. The best SCSI controllers have only three channels, and each channel holds a maximum of seven SCSI devices. So the total is limited to 21 devices, which covers a distance of 15 feet when the devices are daisy-chained together.Steve Rigney, a network analyst at NetReference Inc., said Fibre Channel can scale up to 126 devices and 15 miles. As a result, SANs are likely to be deployed increasingly for data warehousing and electronic commerce.
Although there is much activity and investment in SANs, another year of work is needed before compatibility and interoperability issues are resolved, said Roger Cox, RAID storage analyst at Dataquest Inc., a division of Gartner Group.
Understand Your SAN
As with most new technologies, there is confusion about the definition of a SAN compared with its cousins, network-attached storage and server-attached storage, from which a SAN can be built.
As its name suggests, an SAS is a storage system attached directly to a server. It is the most basic of the three and is not networked.
With NAS, users can go directly to the storage unit attached to the network without having to go through a server. But the higher-bandwidth SAN centralizes storage in a separate network, making it ideal for redundancy, fault tolerance and management of large amounts of data. Some SAS and NAS installations are well-suited for departmental storage needs, but others are early versions of SANs that will evolve as standards mature.
"There's more SAS out there today, some of which will evolve either to NAS or to SANs or both," Dataquest's Cox said. "By 2002, the SAS market will be 55 percent of the total storage market. The SAN portion will be somewhere near 28 percent, and the NAS portion will be 17 percent."
SANs are an emerging market for large and forward-looking agencies. The larger the user, the better the return on investment in a SAN. It is clearly the best solution for organizations with large storage requirements, such as the United Space Alliance, which is responsible for day-to-day operations of NASA's space shuttle fleet.
Mark Hargrove, a member of the technical staff at the United Space Alliance's Platform Architecture Services Group, Cape Canaveral, Fla., said his organization is building a large SAN with 12 Microsoft Corp. Windows NT servers, six Hewlett-Packard Co. Unix servers, a Brocade Silkworm switch and Fibre Channel cable. Hargrove is beta testing Transoft Network Inc.'s SAN Manager for allocating storage among heterogeneous servers. "We are absolutely planning on using it," he said.
With SAN Manager, Hargrove can use a graphical user interface to add and remove storage from Unix and Windows NT servers simply by dragging and dropping storage from one server to another. "There's a graphical [representation] of the storage that allows you to dynamically assign to a server on the fly," he said. "I can literally drag 100G and drop it onto the server, use it on the server, then remove it and assign it to another server without ever having to boot anything. It makes storage management far easier."
But Hargrove advised getting assistance in building a SAN. "If you try to do the integration yourself, you're going to have troubles because Fibre Channel and SANs are still immature, though they are maturing rapidly," he said. Hargrove said Storage Technology Corp. provided him with good SAN integration service.
Waiting for My SAN
Industry experts agree that SANs are far from being simple plug-and-play devices. "You can't just go out and buy any adapter and storage device for your server," said Michael Rowland, director technical operations at SMS Data Products Group Inc., an SAS and NAS provider. "The standards just aren't there in the Fibre Channel community. But in the SCSI environment, you can buy anything, plug it in and it'll work."
There are more than 20 manufacturers of Fibre Channel switches and hubs, and a multitude of vendors selling host bus adapters, also called Fibre Channel interface cards (like PC network interface cards). The lack of standards for SANs, however, has stalled the market until now.
Although most SAN vendors comply with the American National Standards Institute standard for Fibre Channel, software layer incompatibilities arise when they add functionality and drivers beyond the basic application-specific integrated circuits that drive the hardware, said Michael Klein, president and chief operating officer at Transoft.
Because NAS systems standards are already in place, they are more prevalent than SANs. Six months ago, Nellis Air Force Base, Nevada, installed an NAS system composed of Procom's 80G NetForce 100 storage box attached to two Compaq Computer Corp. RAID array systems running Windows NT on an Ethernet network. The NetForce 100, a processor board running a proprietary operating system, supports both protocols for NAS—network file system for Unix and server message block for Windows NT.
"It has given me better management of the data, and it's more accessible to the users," said Donald Wells, senior systems engineer at Nellis. "Before, when users needed the data, they would have to know which drive the data was in. Now all they do is query the system, and it finds the information for them. You can have six drives in a single RAID array, and it looks like one drive to them."
To circumvent the lack of standards, users have installed networked storage systems based on Ethernet, instead of Fibre Channel, to gain the benefits of a SAN without waiting for Fibre Channel standards to evolve. Sandia National Laboratories, Livermore, Calif., is using Ethernet to link its SAN with an HP RAID disk array, HP servers running Windows NT, Cabletron Systems hubs and Cisco Systems Inc. routers.
The initial high cost of buying a large server to set up the SAN was worth it for Sandia, given the alternative. "We have 1,000 users," said Don Hall, a member of Sandia's technical staff. "The cost of 1,000 individual disks exceeds the cost of one large server with mass storage. It's not just the cost of the disk but the cost of time for support people to install 1,000 disks on 1,000 workstations."
Hall recently began testing W.Quinn Associates Inc.'s QuotaAdvisor storage management software, which manages the amount of storage space on individual workstations. "You can segment the storage and predetermine space allocation by users or by directories," said Najaf Husain, W.Quinn Associates' president.
Federal users also are buying ATL Products Inc. systems to begin exploring SANs without fully investing in them. The ATL systems scale from desktop to data center—from one to 16 drives, depending on the application, said Craig Abod, vice president of DLT Solutions Inc., a reseller of ATL products to federal organizations such as the Air Force, the Census Bureau and the Bureau of Land Management.
Abod said the systems will make it easy for agencies to implement SANs when the time comes. "People are moving in the direction of SANs by offloading storage and backup to a separate network, and in this way they are phasing into early implementations of SANs," he said. "These [ATL] systems are SAN-ready—you just add the Fibre Channel controller card—so there's real investment protection."
With products being shipped to help users set up preliminary versions of SANs, and with Fibre Channel standards looming over the horizon, now may be the time for agencies to take a look at this emerging technology.
-- Gerber is a free-lance writer based in Kingston, N.Y.
AT A GLANCE
* Status: Some forward-looking agencies have begun installing storage-area networks to reduce traffic on their local-area networks. However, most agencies have not yet delved into SANs, though some have installed rudimentary versions of the technology.
* Issues: Many users have postponed SAN installations while the industry creates standards for Fibre Channel data transfer architecture, a necessary ingredient for SANs. The lack of standards has made SAN installation extremely complex and has limited capabilities for tasks such as file sharing or running Transmission Control Protocol/Internet Protocol over Fibre Channel.
* Outlook: Positive. Though SANs are still rare within the government, agencies appear to be preparing to embrace the technology once standards are in place. Users are starting to build network-attached storage or server-attached storage architectures that eventually will evolve into SANs.