Storage Area Networks Take Two Steps Forward

By Curt Harler | Aug 15, 2002
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The latest buzz in the low-voltage market is Storage Area Networks (SANs). SANs began in a mixed environment, and contractors had to deal with different host bus adapters and different configurations. Resolving compatibility problems often involved calls to numerous vendors.

That is changing. Contractors will be relieved to hear of success by several vendors who agreed to assure interoperability.

In simple terms, a SAN is an electronic library that can be accessed from any computer. Data goes to the library and is accessed later by users. In more technical terms, a SAN is a network whose primary purpose is transfer of data between computer systems and storage elements and among storage elements.

SAN vendors celebrated the New Year with two agreements making SANs more flexible for users and easier for contractors. Brocade Communications Systems, Compaq Computer, Emulex, IBM, JNI and QLogic rolled out a solution for an open, standards-based SAN. Theirs is the first multi vendor solution to be accepted and approved by the Supported Solutions Forum (SSF) under its new submission and registration guidelines.

In short, a contractor may feel a particular problem is due to the IBM component, but the IBM help desk feels it really is a Compaq problem. Rather than send the contractor off to Compaq, IBM’s support team will contact Compaq directly to get a solution.

“This is not a how-to, cookbook-style solution,” Marc Oswald, SSF chairman said. Rather, SSF lists firmware versions and configurations supported by vendors.

The SAN design features a redundant fabric enabling a fault-tolerant network with dual-path and host bus adapter (HBA) fail-over capability. Simultaneous data backup and recovery capability is supported with IBM’s Tivoli Storage Manager. Other third-party offerings are available.

If the world is ever to reach the Holy Grail of the “paperless office,” people will have to have confidence that they can store and retrieve data without writing it down and printing it out. Such reliable, fault-proof data storage is among the SAN’s main functions.

In late January, the Storage Networking Industry Association (SNIA) and the Technical Support Alliance Network (TSANet) announced another agreement to use TSANet’s multivendor support process. This, too, will make life easier on contractors who troubleshoot SANs. Rather than having to negotiate support agreements with several vendors, contractors can join a single support community and be assured of 24/7 service that meets TSANet’s Code of Conduct.

Equipment first used in SANs was a single-vendor solution. But customers wanted “best of breed,” and SANs became notoriously heterogeneous. This led to a number of issues an installer had to address before turning the SAN over to the customer.

SANs consist of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements and computer systems so that data transfer is secure and robust. It is the physical part that most interests electrical contractors.

Just about any of the high-powered physical-layer networking technologies can be used to connect all of the elements of a SAN. Contractors who are familiar with Fibre Channel, fast Ethernet or Gigabit Ethernet, Myrinet, VAX’s CI network or ServerNet will feel at home with most SAN architectures.

Of absolute importance in wiring any SAN is to provide as much redundancy in the network as possible. This will allow communication to continue even if one or more components on the network fail.

At the heart of the network is a host computer. The host typically attaches to a SAN with an HBA or network interface card. Either will be supported by an assortment of software drivers.

There can be several host computers on a SAN. A host is not a storage device, but a computer front-end that has its storage needs met by other hardware on the SAN. Hosts can either operate cooperatively, or they may be largely unaware of one another.

Physical devices that make up a SAN include the disk drives and disk arrays, storage controllers, tape drives and tape libraries and any one of a number of storage appliances. Cooperation typically occurs across a “cluster,” which is a subgrouping of storage devices.

Advise the customer to opt for separate hosts. The way networks grow, it is reasonable to expect that there will be different hardware architectures and versions or types of operating systems involved.

Design any SAN for redundancy––even to a seemingly ridiculous degree. Redundant connections within an interconnect may enable the network elements to continue to provide service by directing traffic around the failed components. Popular network protocols include such commonplace ones as small computer system “scuzzy” interface (SCSI), file control protocol (FCP), transmission control protocol/Internet protocol (TCP/IP), virtual interface (VI), CIFS and network file system (NFS). They are referred to almost always by their acronyms.

Oswald promised several more configuration and vendor agreements. EC

HARLER, a frequent contributor to ELECTRICAL CONTRACTOR, is based in Strongsville, Ohio. He can be reached at 440.238.4556 or [email protected].

About The Author

Curt Harler, a frequent contributor to SECURITY + LIFE SAFETY SYSTEMS, is based in Strongsville, Ohio. He also can be reached at 440.238.4556.





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