With so many HBA features, knowing which ones matter and which ones don't can be a challenge for just about any administrator. Here's a short description of some of the features shipping today that may influence your buying decision.
DATA BUFFERS. Data buffers serve as a necessary and valuable component of Fibre Channel (FC) HBAs, but they shouldn't be thought of as a differentiator when selecting an HBA. This feature primarily becomes important in long-distance SANs, as higher buffer credits are needed to accommodate the longer latency periods when the data is sent and received.
FC SPEED. Two-gigabit FC HBAs are now available from every HBA vendor and make up the majority of HBA sales. They still autosense down to 1Gb to work with existing environments. The road map for next-generation HBAs is still uncertain, but 4Gb appears likely because, unlike 10Gb FC, it is backward-compatible with 1Gb and 2Gb FC, and will cost about the same as the 2Gb cards shipping today.
WWN SPOOFING. World wide name (WWN) spoofing is an interesting feature, but it has only limited application in today's SAN environment. Most HBA vendors offer it for customers who request it. Vendors see this feature primarily used in clustered server environments and feel the increased security risks outweigh the potential benefits of this technology.
CONTEXT SWITCHING. Context switching also serves as a necessary and valuable component of FC HBAs, but again, it shouldn't be thought of as a differentiator when selecting an HBA. This feature primarily takes on importance when the speed in routing a FC packet is a factor and SANs are already running at high capacity.
LOAD BALANCING/MULTIPATHING. These interrelated features serve as a requirement for any highly available server. Load balancing will balance the FC traffic over two or more paths through the SAN, while the multipathing feature enables the operating system to have more than one path to disk, should one HBA fail or a path through the SAN becomes unavailable.
CIM COMPLIANCE. Charles Kraus, HBA business unit director of Milpitas, CA-based LSI Logic, sees CIM functionality as one of the critical new features all HBA vendors must now offer. This feature will permit the management of heterogeneous SANs and enable certain functions (such as performance monitoring, remote firmware and driver upgrades and troubleshooting) across all HBAs, regardless of vendor.