Protocol options lead to 'storage-agnostic networks'

With the confluence of Fibre Channel, IP/iSCSI, and InfiniBand, the "one-size-fits-all" rule won't apply in the storage networking arena.

By Greg Schulz

Over time, we have seen a shift from proprietary storage interfaces on mainframes, midrange systems, and PCs to more open interfaces like parallel SCSI and, more recently, to Fibre Channel and FICON storage area networks (SANs).

There is considerable debate about protocols and interfaces, leading to "storage interface wars" that break out every few years as new technologies surface. It seems like just yesterday that it was SAN versus network-attached storage (NAS), Fibre Channel vs. SCSI, and Fibre Channel vs. SSA (IBM Serial Storage Architecture). The convergence of SAN and NAS products from a variety of established vendors and start-ups has for the most part left the SAN vs. NAS debate smoldering, although there are still some minor flare-ups.

The adoption of Fibre Channel as an enterprise-class storage networking interface has silenced the SAN interface wars of the mid- and late 1990s. Now a new battleground is developing, pitting Fibre Channel against Gigabit Ethernet and IP (iSCSI) and, eventually, InfiniBand.

While Fibre Channel has proven to be the dominant SAN interface, current implementations often result in complex, expensive fabrics that are difficult to manage, giving plenty of ammunition to the anti-Fibre Channel camp.

Flexible, scalable Solutions
While it is interesting to watch the polarization among the various camps, end users are primarily concerned with obtaining flexible, stable, and scalable solutions. Fibre Channel, iSCSI, and InfiniBand, along with other emerging technologies, are new implementations under the larger, more all-encompassing storage networking umbrella. The focus should not be on one vs. the other but, rather, on how they complement each other so that global storage networking can address today's business challenges and future demands as the amount of data grows and technologies mature.

We have already seen the SAN vs. NAS debate subside, because they are complementary techniques for accessing data in a storage networking context. Soon we will also see more examples of how iSCSI and FCIP (or iFCP) can be used to build larger, more-global storage networks comprising smaller interconnected SANs. We should also see how iSCSI uses block-level storage access to solve low-end and departmental backup and storage problems. Furthermore, iSCSI will be used to bridge local and remote SANs. iSCSI and other new technologies will eventually bring storage networking to the masses.

In addition, FCIP (or iFCP) will enable consolidation of local and remote Fibre Channel SANs using multiple upper-level protocols (ULPs) like SCSI over Fibre Channel (FCP), IP over Fibre Channel (IPFC), and Virtual Interface Architecture (VIA) over Fibre Channel.

With 64-buffer credits per port available on large directors today, Fibre Channel and FICON can be extended to distances of 80km with long-wave GBICs, and beyond 100km with dense wavelength-division multiplexers (DWDMs). In addition to Fibre Channel extension, DWDM is also a good platform to support Gigabit Ethernet, ESCON, FICON, ATM, and other network interfaces over metropolitan optical networks. Other options are SONET and optical networking solutions (e.g., mapping Fibre Channel directly onto SONET [FCBB and FCBB2] to eliminate the overhead associated with IP).

The role of InfiniBand should become clear this year to enable new and larger applications as well as storage networks to overcome current PCI performance issues.

In the end, it will be clear that these technologies are all complementary and that SANs should be renamed "storage-agnostic networks" (with NAS becoming "network-agnostic storage").

As more and more technologies become available, don't accept a "one-size-fits-all" strategy for storage networking. After all, look at your networking infrastructure and you'll probably find a mix of Ethernet, FDDI, ATM, and other interfaces and protocols.

We are entering the next phase of the evolution in storage networking, where we have different interfaces for different applications. This will enable you to apply the right solutions for specific application requirements, as opposed to doing everything with just Fibre Channel or IP. Storage networking is more comprehensive than just a Fibre Channel SAN, an iSCSI SAN, or an InfiniBand SAN. A true enterprise storage network should be protocol/interface-agnostic.

Greg Schulz is director, storage networking solutions, at Inrange Technologies (www.inrange.com) in Lumberton, NJ. He can be reached at greg.Schulz@inrange.com.

This article was originally published on May 01, 2002