Network storage & SANs

By J.B. MilesSpecial to GCNThe year of the SAN has arrived, representing a milestone in storage technology with major implications for government agencies that need to turn terabytes of data into useful information for perhaps millions of users.As the government continues to go paperless, the digitized data that information services departments must handle has grown to mammoth proportions. The first line of defense against total systems meltdown is storage technology, said Mark Vaccarino, director of system integration technologies for V-Squared, a federal application service provider in Ashburn, Va.'Today's organizations require huge amounts of data storage, and the systems themselves must be highly scalable and upgradeable,' Vaccarino said. He agrees with other experts that storage area networks meet these criteria better than any other storage technology currently available. And he predicts SANs will account for the next big mass migration of government and private organizations to all-in-one storage environments.In typical server-attached storage designs, storage arrays are tightly linked to servers. The design is effective when storage requirements are limited, but not very cost-effective or efficient when storage needs soar into the terabyte range because new servers must often be purchased to manage additional disk or tape storage devices.SANs provide access between servers and a pool of shared storage devices by utilizing 1-Gbps Fibre Channel links between devices'and 2-Gbps Fibre Channel is on the way. For information services departments, the big payoff from a SAN is that any user connected to any server on the network can gain access to information on any of the storage systems in the pool.SANs free up server CPUs to perform other computing tasks. They also offer round-the-clock availability, with built-in redundancy for improved data security. And advanced software has made most SANs highly scalable.SANs can be as simple or complex as your requirements dictate, but it helps to keep in mind the basic components that make them up. In theory, any server can connect to a SAN, but mainline computer makers such as Compaq Computer Corp., Dell Computer Corp., IBM Corp. and Intel Corp. provide specialized SAN products. A SAN system could be a redundant array of independent disks, a loosely structured just-a-bunch-of-disks arrangement, a CD-ROM disk array or a tape library. Check with leading storage vendors such as Advanced Digital Information Corp., Dot Hill Systems Corp, Hewlett-Packard Co., Exabyte Corp or Storage Technology Corp. to see which of their products are SAN-enabled. If economy, rather than scalability, is your top priority, and you are setting up a fairly small SAN for workgroup service or for a small department, a Fibre Channel hub could provide an inexpensive solution.Hubs offer a high degree of multivendor interoperability because in most cases physical addressing is transparent. Unmanaged hubs can be cost-effective in some situations, with a few products such as High Velocity System's Bullet 600 coming in at slightly less than $100 per port.Virtually all hubs used in a SAN architecture support the Fibre Channel Arbitrated Loop (FC-AL) configuration, which provides an aggregated, or shared, bandwidth of 100 Mbps. Although FC-AL hubs can support up to 127 attached devices, far fewer are recommended in most cases to avoid conflicts that can dramatically slow data throughput.The Fibre Channel hubs listed in the accompanying table include both managed and unmanaged versions, and generally support between five and eight ports with both DB-9 copper and gigabit interface converters (GBICs). Most of them come with LED indicators and diagnostics software to help isolate faulty ports and drop them from the loop before they bring a hub's performance to a halt.In addition to service as backbone devices for small SANs, Fibre Channel hubs also can be used as low-cost companions to switches in complex, multitiered SAN designs. Fibre Channel switches are a must for large SANs that store terabytes of information. Although many switches can provide both point-to-point and FC-AL configurations, high-end versions are nonblocking fabric switches. They guarantee full-speed data delivery regardless of traffic conditions and employ all or most of the Fibre Channel methods for linking nodes and routing frames in a multiswitch Fibre Channel network.Vixel Corp.'s 7100 and 7200 switches are cost-effective entry-level models that can be upgraded to the company's full-fabric 8100 switches. Brocade Communications Systems Inc.'s SilkWorm 2000 family is similarly expandable, with the entry-level 2010 model supporting FC-AL configurations, and the high-end 2040 model supporting entry-level SAN fabrics. Both the 2010 and 2040 can be upgraded to the SilkWorm 2050, a robust device for multiswitch full SAN fabrics.Virtually all switches can be managed with software from the switch manufacturer or from third parties.Gadzoox Networks Inc.'s Capellix 2000 and 3000 switches are managed with the company's Ventana SAN Manager. Vixel supplies SAN InSite 2000 management software with its switches. Brocade installs its Fabric OS, which includes Fabric Watch for simplified SAN management and Extended Fabrics for extending SAN-to-SAN connectivity distances.Most Fibre Channel switches come in eight- to 16-port versions. A few, such as McData Corp.'s 32-port ED-5000 and Ancor Communications Inc.'s SANbox-64/128, are director-class switches with high port densities that are designed to direct the activities of other switches and hubs in three-tier SAN architectures. Like standard 10/100-Mbps Ethernet cards in other parts of a network, Fibre Channel host bus adapters are the essential elements of SAN systems. These small but necessary components go into the servers and other network hardware to make them part of the SAN.In fabric configurations, host bus adapters provide a fabric log-on to initialize the servers and then scan the entire arbitrated loop to initialize the other devices on the SAN.If data is being streamed from multiple storage pools into a particular server, the host bus adapters also perform context switching to help reduce traffic overhead.When selecting the appropriate Fibre Channel host bus adapter, it's important to check for compatibility with host buses, such as PCI or MCA, operating systems and the types of connectors'DB-9 copper or GBIC optical'required. Although virtually all host bus adapters support full-duplex throughput of 100 Mbps, a few, such as Emulex Corp.'s LP8000DC and Interphase Corp.'s 5550 PowerSAN, are dual-channel cards that effectively double typical 1.0625-Gbps full-duplex data rates for high-throughput storage requirements.QLogic Corp., which holds the leading share of the Fibre Channel host bus adapter market, and other leading companies such as JNI and Emulex provide robust suites of software drivers and remote configuration and management utilities to make their products suitable for service in just about any SAN.Software is the tie that binds the collection of equipment making up a typical SAN. Most switch and hub vendors offer proprietary management software, and customers increasingly are looking for ways to manage heterogeneous SAN components.The result is a ballooning market for storage management software, according to Dataquest, the San Jose, Calif. subsidiary of the GartnerGroup Inc. of Stamford, Conn. The market research company recently reported that worldwide storage management software revenues were $4.2 billion last year, a 47 percent increase over 1998 revenue, and predicted that revenues will soar to $14.7 billion in 2004.This guide includes more than 25 software products () useful for managing a wide variety of SANs. Some, such as Data General Corp.'s Navisphere, Dot Hill's SANman suite and Gadzoox's Ventana, are designed primarily to manage each company's proprietary line of servers, switches or hubs.Others are designed to meet more general storage requirements.Computer Associates International Inc.'s ARCserveIT Enterprise Edition offers built-in SAN management capability via the company's Unicenter TNG Framework.SANsymphony from DataCore Software Corp. provides enterprise-level network storage pooling across heterogeneous SAN components. It comes in both an entry-level Server Edition and a full-function Network Edition.Hewlett-Packard's SureStore E SAN Manager comes in two flavors: DM provides centralized device management for a variety of manufacturers' hubs and switches; LM offers logical unit management of hundreds of host devices.IBM, pre-eminent among providers of integrated SAN products with its own brand of servers and storage units, has Tivoli SANergy File Sharing, software that enables the sharing of SAN arrays, file systems and files across multiple systems. The company plans to release other SAN software products later this year.The Storage Networking Industry Association, whose Web site is at , offers the following criteria to guide your selection of SAN management software: SAN software must account for a large number of components and a multitude of physical and logical relationships between them. Software should include the tools for providing a system-level view of overall SAN performance. Software and firmware updates should be managed from a centralized station, and a generic mechanism should be provided to transport updates to components from different vendors. Capabilities such as standardized SAN resource identifiers containing asset information must be defined. The software should include a common mechanism to obtain asset information from SAN resources. Managing SAN clusters requires robust solutions for workload management and a single point of control for the cluster's component systems. The software should support both data and storage management within and across clusters. A centralized manager must become a trusted entity to manage isolated storage devices and zones. Examples of services that require policy are disaster recovery, backup, hierarchical storage management and archiving.XXXSPLITXXX-XXXSPLITXXX-XXXSPLITXXX-