Karl Paulsen /
07.06.2005 12:00 AM
Fibre Channel Fends Off Competitors
Fibre Channel data rates are about to double--again. This 10-year-old server and storage connection technology has grown from 1 Gbps to 2 Gbps, and now products are available that bridge the 4 Gbps domain.

The impact of these advances on media server storage systems is in the added bandwidth for large-scale SAN configurations. The ability to provide disk throughput is perhaps the highest priority for large blocks of streamed or FTP'd data in media server architectures.

Fibre Channel connection technologies are more flexible and at least three times faster than SCSI, which is restricted to short-distance cabling and parallel interfaces. Speed and flexibility make Fibre Channel far more practical for medium- to large-scale storage systems. It can be deployed in point-to-point, switched and loop interfaces; and it is designed to interoperate with SCSI, Internet Protocol and other protocols.

In its early implementation, Fibre Channel was badmouthed, often plagued by differences in the interpretation of specifications between disk drives, controller interfaces and other components. Those early incompatibility issues have all but vanished, clearly placing Fibre Channel into the mainstream for modern storage architectures.

BORN IN PRE-PRESS

It was the prepress industry in the mid-1990s that hailed Fibre Channel because the technology enabled large image files to be moved between workstations and specialized processors for printing.

In the early years, designs for fault-tolerant mechanisms that could reroute around failed cable loops signified one of its principal advantages. Yet many years passed before those capabilities were properly applied to a transparent failover architecture supported in software.


(click thumbnail)
Fibre Channel, based on specs in the Fibre Channel Physical and Signaling standard, can be found under ANSI X3.230-1994, aka ISO 14165-1.
Some first-generation video servers employed shared storage across multiple channels by using dual-arbitrated loops that enabled this transparent failover concept. The concepts were effective, and it marked the beginning of what is now a universally accepted architecture for storage industrywide.

Fibre Channel connectivity has grown significantly. For short-distance interfaces, Fibre Channel interconnections can be deployed on coaxial cable or UTP (unshielded twisted pair) cabling, and now these interconnections can be separated by a much as 10 kilometers when connected over optical fiber.

In campuswide implementations, Fibre Channel further enables the consolidation of high throughput to centralized storage--a topology now widely deployed and accepted in massively large media server storage systems.

In a parallel development path, and before the widespread acceptance of storage area networks (SAN), the predecessor, network attached storage (NAS), employed Ethernet. Unfortunately, NAS, with its low 10 Mbps throughput, made Fibre Channel unsuitable for many applications when compared to direct attached storage (DAS), which was upwards of 20 times faster at the time.

REACHING 10 Gbps

There is now clear evidence that both Fibre Channel and SANs are here to stay. Around mid-2004, 1 Gbps Fibre Channel platforms were squarely headed toward a 2 Gbps storage and distribution transition.

But by the time this transition was firmly rooted, several manufacturers had already started to demonstrate host bus adapters (HBA), disks and switches that could operate at 4 Gbps. Today, some startup manufacturers are already dabbling in 10 Gbps Fibre Channel!

As mentioned, Fibre Channel technologies are particularly important to the SAN. To implement a dedicated, high-performance storage network with high-volume data transfers, Fibre Channel's high transfer rates become critical to success. Given that a SAN can have a high degree of sophistication, management complexity and cost, most large-scale SANs are traditionally implemented for mission-critical applications in the enterprise space.

Systemwide storage area infrastructures that connect storage devices (NAS, DAS, RAID arrays or tape libraries) to servers now generally employ the gigabit technologies found in Fibre Channel.

Using Fibre Channel, server/storage combinations enable simultaneous communication among workstations, servers, data storage systems and other peripherals--free of the distance and bandwidth constraints of SCSI.

While DAS and NAS are generally optimized for data sharing at the file level, SANs are superior in their ability to move large blocks of data. It is this combination of SAN/Fibre Channel technologies that enables the kind of bandwidth-intensive transfers found in media-centric applications.

These same principles are similarly applicable to activities such as database, image and transaction processing. Furthermore, the SAN enables a distributed architecture that offers the highest levels of performance and availability, better than other storage mediums available.

A SAN, in concert with Fibre Channel connectivity, also will dynamically balance loads across the network, a key to providing fast data transfer with reduced latency at the I/O level. For media server applications, this permits large numbers of users (i.e., encoders, decoders and workstations) to simultaneously access centralized data without creating bottlenecks.

That's not the end of the story. Today, those advantages originally found only in Fibre Channel continue to blur as other technologies adopt similar attributes (e.g., Gigabit Ethernet, iSCSI and more). For example, on a campuswide level, iSCSI offers identical performance for common tasks such as backup.

Still, confusion continues whereby the term "SAN," which originally applied to a Fibre Channel connected network, has become de-emphasized by its common usage. So now we add confusion with the terminology of "IP-SAN," which usually refers to iSCSI and uses Ethernet and not Fibre Channel as the underlying transport in a local area network.

The battle between Fibre Channel and iSCSI will continue to brew because even though iSCSI is cheaper, 4 Gbps Fibre Channel is faster. That said, those differences may diminish as 10 Gbps Ethernet development and the port cost for switches drop.

PRICES COME DOWN

It was only recently that 10 Gigabit Ethernet carried a hefty price tag, but as production begins to ramp up, the new 10 Gbps products will make for a higher volume push into the Fibre Channel arena, yielding a more compelling reason to consider iSCSI deployment.

These kinds of trends continue. Media servers are now pretty much standardized with Fibre Channel storage connectivity, Gigabit Ethernet interfaces for file transfers, and 300-plus GB hard drives. The switches that integrate these connections are also part of the total cost of deployment.

Consider that only four years ago, the cost-per-port for a 10 Gbps Ethernet switch approached $50,000; two years ago that price dropped to $5,000. Industry forecasts for 2005 suggest the price will reduce to around $1,000 per port. By contrast, the cost-per-port for a 4 Gbps Fibre Channel enterprise-level switch looks to be only about $800 to $1,200.

It's clear that as media server technologies evolve into much larger mass storage devices, the current practice of separating low-resolution images from full-bandwidth pictures is less certain, and "online" versus "offline" seems to get fuzzier.

At the point where the image size in terms of bits becomes inconsequential, this can only produce positive results for the media content creation and distribution industries. The recent trend toward low entry-cost high-definition production may now become more accelerated as storage bandwidth increases and the costs decline.


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