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8Gb/sec Fibre Channel widens lane for SAN traffic

The need for more Fibre Channel (FC) bandwidth continues unabated, driven by server and storage virtualization, and data replication. To meet these new demands, 8Gb/sec FC switches and host bus adapters (HBAs), along with enhanced software integration with virtual servers, are set to debut in 2008.

Richard Villars, VP of storage systems research at Framingham, MA-based IDC, finds that server and storage virtualization, as well as better utilization of multicore and bladed servers in data centers, are priorities for IT executives. "The concentration of server and storage assets makes the delivery of higher speed solutions like 8Gb/sec Fibre Channel critical for companies that want adequate network capacity in their data centers," says Villars.

Scott McIntyre, Emulex's VP of software and customer marketing, says that even though 4Gb/sec FC was released in 2005, customers continue to display an "insatiable demand" for more network capacity. He speculates that the rapid adoption of server virtualization could lead to companies buying servers that support the new PCI Express (PCIe) 2.0 computer expansion card interface.

Emulex's new 8Gb/sec FC HBAs, scheduled to ship in the first half of 2008, take advantage of the PCIe 2.0 interface to support higher throughput on server IO backplanes. "IO backplanes are often underutilized on these servers," says McIntyre, "but as customers create more virtual machines, they drive up utilization."

Server virtualization is driving the need for 8Gb/sec FC, as well as enhanced VMware support for N_Port ID Virtualization (NPIV). Using NPIV, VMware can assign specific virtual world wide name (WWN) numbers to virtual machines (VMs) so each VM can only access storage assigned to that WWN on the FC SAN. Many FC switches and HBAs already support NPIV, but VMware doesn't yet automatically assign specific virtual WWNs to VMs.

The next release of VMware ESX, currently in beta, natively supports NPIV and dynamically assigns virtual WWNs to VMs. Emulex's FC HBA drivers, which support NPIV, are being tested with ESX and going through VMware's approval process. "There is a lot of pent-up demand among ESX shops for NPIV," says Emulex's McIntyre.

Mario Blandini, Brocade's director of product marketing, advises companies to verify which older FC ports they're using in their FC SAN before upgrading. While 8Gb/sec FC HBAs and switch ports are backwards compatible with 1Gb/sec, 2Gb/sec and 4Gb/sec FC HBAs and switch ports, some older devices may require you to program the switch port to a fixed port speed.

"The optical connector changed from SC to LC connectors when 2Gb/sec FC was released, so the correct cable is needed for connecting 1Gb SC to 8Gb LC," says Blandini.

Doug Ingraham, senior director of SAN product management at Brocade, says the firm is updating its FC switch management software as new 8Gb/sec FC director blades are released to improve support for virtual server environments. Brocade released a new 16-port 8Gb/sec director blade for its 48000 Director in October 2007 to aggregate a greater number of VMs on a single FC port. Brocade finds that oversubscription on 8Gb/sec FC ports can still occur in environments where VMware's VMotion is used.

VMotion can move VMs from one physical machine to another to perform transparent, nondisruptive server migrations. For the migrations to appear transparent to the application, there must be sufficient server and SAN capacity available on the target server. Brocade's Fabric OS analyzes the workloads of the source and target physical servers' FC ports. It then communicates these readings to VMotion so VMotion can make a determination about where to migrate the VM.

"If you initially choose to migrate from server A to server B, it might tell you that migrating to server C is a better idea," says Ingraham.

--Jerome M. Wendt

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