Advances in Network Storage Access Offer New Options

Corporate storage managers tend to make strategic and technology infrastructure adjustments in timeframes of five to seven years, which lets them deploy new storage technologies while preserving infrastructure that has worked reliably for years.

It is unlikely that storage managers are going to modify that approach and start making changes at Internet speed. But there are advances in storage access technologies making their way onto the field that promise to help data center managers more capably deal with virtualization, green initiatives, speed, performance, and total cost of ownership. In addition to existing options like Fibre Channel and iSCSI, additional data center storage infrastructure alternatives making noise include Fiber Channel over Ethernet (FCOE) and 6 gigabit per second Serial Attached SCSI (6 Gbit/s SAS). All of these options will be part of data center planning topics in the next year or two.

FC, FCOE, iSCSI, and 6 Gbit/s SAS each have their own value propositions, which makes it imperative for data center managers to understand where their data infrastructures are headed, the needs of mission-critical applications, what effect new directives like virtualization will have on storage needs, and how best to manage asset acquisition and retirement cycles. Depending on the mix of storage access technologies implemented, staffing requirements and data center cultures could also change.

"I think that we will continue to see large enterprises use Fibre Channel technology, since they already have major investments there," said Dennis Martin, president of Demartek , a technology research and test center. Martin estimates that 80 percent to 90 percent of large enterprises are already using Fibre Channel, and that's not likely to change. The same organizations are likely to affect gradual transitions into FCOE, which will let them run a single converged IP network for storage and networking and evolve to 10-Gigabit Ethernet. "This will greatly accelerate access as networks converge, especially when you consider that as 8-Gigabit FC enters the market today, most sites have not even driven the 4-Gigabit FC very hard yet," said Martin.

Some vendors and blogs have claimed that less expensive iSCSI can meet high-performance storage access needs as capably as Fibre Channel, and some even have predicted that iSCSI will displace Fibre Channel. But Martin has a different perspective."People who say that one technology will be dominant over another seem to be coming from a certain market mindset [smaller businesses] without being aware of others [large enterprises]," he said. "They also do not seem to be aware that in the storage world, churn of infrastructure is very slow. Both Fibre Channel and iSCSI will be around for the long haul because both address different sets of needs."

Small and midsized businesses have embraced iSCSI because of its relatively low cost, and they're hiring people with IP expertise, but not people with FC expertise. "They don't want [them] because they don't have FC investments, said Terri McClure, an analyst with Enterprise Strategy Group (ESG) . If iSCSI were to displace Fibre Channel, McClure said, it would require "a very long transition that takes into account investment directions that companies already have in place."

Not surprisingly, Skip Jones, chairman of the Fibre Channel Industry Association (FCIA) , agrees.

"There's always going to be some overlap and controversy, but the fact is Fibre Channel and iSCSI each have their own markets," said Jones. "Fibre Channel continues to be strong in 85 percent to 90 percent of large enterprises that have a storage-centric culture constructed around SANs wired with Fibre Channel. They already have ease of use and proven performance. There isn't a need to upgrade."

This brings us to technology upgrades like 6 Gbit/s SAS, which is fully compatible with SATA (serial advanced technology attachment) drives and can run in FC, FCOE, or iSCSI environments."The promise of the technology is 600-Mbit/s access speeds and dramatically improved performance and manageability of SAS storage," said Cameron Brett, manager of product marketing for PMC-Sierra, a 6-Gbit/s SAS provider. "With 6-Gbit/s SAS, you can preserve your existing infrastructure, but also be in a position where you can add faster, more manageable SAS connections. One area where we see sites using 6-Gbit/s SAS is for small storage fabrics contained within a rack-mount system."

Regardless of their infrastructure topologies, the time for sites to start thinking about advanced storage access is now. With higher access speeds and attractive new features like built-in diagnostics and self-discovery inventory-taking on expanders, 6-Gbit/s SAS will be incorporated into storage product offerings beginning in first half of 2009.

Businesses will continue to choose between implementing Fibre Channel and iSCSI, depending on their size and needs. In smaller branch offices that don't use Fibre Channel, iSCSI may hold sway. Another option for branch offices and small companies is "SAN out of the box" products that FCIA's Jones describes as an affordable way to implement Fibre Channel with a "set of agreed upon industry behaviors for a small SAN."

At the same time, large enterprises, which typically have separate storage and network staffs, will continue to undergo cultural change as trends like virtualization change the demands placed on networking and storage systems. These groups will have to work with each other to facilitate best-of-class results in a converged storage environment that runs on IP.

"Data centers are all looking at data growth, virtualization, and consolidation," said Martin. "The good news is that all of these storage access technologies address these issues with new interfaces, and all will bring data access more capability. In the end, it's really a matter of what is the best fit for the data center's long term business goals."0