Switches

A network switch is a small device that joins multiple computers together at a low-level network protocol layer. Technically, network switches operate at layer two (Data Link Layer) of the OSI model.

Network switches look nearly identical to hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately. By delivering messages only to the connected device that it was intended for, network switches conserve network bandwidth and offer generally better performance than hubs.

As with hubs, Ethernet network switches are the most common. A network switch offers differing port configurations starting with the four- and five-port models, and support 10 Mbps Ethernet, 100 Mbps Ethernet, or both.

When buying Fibre Channel switches, be aware that any product not sold by one of the six aforementioned companies is an OEM version. EMC Corp. and IBM, for example, both resell other manufacturers' switches; the Brocade SilkWorm 12000 is sold by IBM as the IBM TotalStorage SAN Switch M12. Vendors might need to be prodded to release information about OEM versions.

The Fibre Channel switch market architecture is similar to that of the Ethernet switch market. On the top end are director-class switches dominated by McData, which is followed closely by Inrange and, most recently, Brocade. In the middle is the workgroup class of switches led by Brocade. The dying bottom of the market, comprising the Fibre Channel hub, is a standardized commodity sector dominated by Gadzoox and Vixel.

Before adding a Fibre Channel switch to your SAN (storage-area network), you must ascertain if your company is using 1-Gbps or 2-Gbps Fibre Channel equipment. If you purchased your Fibre Channel implementation in the past 12 months, you probably opted for 2 Gbps, which is top end for today's Fibre Channel systems. If you're using 1 Gbps, however, you have to decide if your bandwidth throughput needs might rise to 2 Gbps, necessitating an upgrade. If you think that's likely, purchasing a 2-Gbps switch may be the way to go, even if the rest of your SAN, including HBAs (host-bus adapters) and disks, is not yet capable. Speedwise, 2-Gbps switches are backward compatible, so they'll revert to 1 Gbps if they encounter 1-Gbps equipment.

Gourmet Switches

Director-class switches offer the ultimate reliability and port density. In a data center with large amounts of Fibre Channel infrastructure, these products function as almost bulletproof, centralized storage switches. Redundant data paths, redundant power supplies and nondisruptive code load are the hallmarks of this equipment. Nondisruptive code load allows you to update firmware without stopping the flow of data to the switch. This defines director-class reliability, as changes to the low-level code of a switch happen relatively often.

Although McData and Inrange have good products in this space, Brocade's recent release, the SilkWorm 12000, raises questions. Some common features of director-class switches, such as the nondisruptive code load, are missing in the SilkWorm switch. Brocade says this functionality will be available at year end, so if you're already using Brocade's products--either supplied by Brocade or as another vendor's OEM equipment--and you are planning to purchase Brocade's director-class switches, we recommend waiting until the features ramp up to meet the class expectations.

Crowd Pleasers

Workgroup Fibre Channel switches are numerous and more versatile. You can use workgroup switches in many ways, the most obvious being on a small SAN. These switches can be connected for greater port counts through interswitch links, which can be created on any port on a Fibre Channel switch. If you plan to mix vendors, however, make sure your equipment will interoperate.

Port count and cost per port are important considerations at the midrange level. Check out our pricing chart for 16- to 18-port 2-Gbps Fibre Channel switches (graphic), as these key pieces of equipment can be expensive.

If you're assessing switches below the director class, you should be considering only high-availability products. For companies that need to have their SAN up at all times, redundant links and redundant switches are essential--two Fibre Channel HBAs in each server with one connection going to each switch. You should also have two interswitch links between each switch and two connections to each attached storage device--one on each switch. This can lead to a proliferation of switches or directors and a dramatic cost increases. However, the reliability gained from this type of configuration in all but the smallest of implementations makes the investment worthwhile. For institutions such as financial services and health care, redundant configurations are a must.

No-Frills Fare

We don't recommend using devices at the bottom end of the Fibre Channel market--hubs--unless your company is very small or has serious budget constraints. You may encounter some manageability problems with these low-end devices, and Fibre Channel switches are becoming an ever-more preferable alternative as switch prices drop.

That said, if you're set on choosing Fibre Channel hubs, here is some information to help you make a smart selection. Hubs come as small as six ports, such as the Gadzoox Gibraltar GL; midsize, such as the seven-port Vixel 1000 and eight-port Vixel 2100; and large, such as the 12-port Gadzoox Gibraltar GS. Some hubs have the ability to do limited zoning, and the Vixel 2100 can create up to four separate FC-AL (Fibre Channel Arbitrated Loop) "zones." The main thing that distinguishes a hub from a switch is that, as with Ethernet, a hub creates a shared point-to-point FC-AL medium.

Hubs essentially concentrate cabling, provide minimal management and do cable conversions through the installable GBICs (Gigabit Interface Converters) they employ. These devices are bandwidth limited and do not offer the fabric that Fibre Channel switches provide.

Whether you're moving to 2 Gbps, upgrading a class or simply maintaining or expanding an established switch structure, the six companies selling Fibre Channel switches and hubs can meet your most specialized needs. Just be sure to choose a product you can live with for a while, at least until the compatibility issues with Fibre Channel switches are resolved.

Makes Available For Switches