In the Fibre Channel (FC) world, a host bus adapter (HBA) provides an interface that interconnects servers, switches and storage devices on the fabric. Servers typically employ HBA cards that are inserted into PCI-X or PCIe motherboard expansion slots. The expansion card approach offers a modicum of expandability and a simplified upgrade path. That is, HBAs can be upgraded when a card with faster ports and better features becomes available. By comparison, many dedicated storage subsystems and appliances may include HBA connectivity directly on the mainboard (aka backplane). This simplifies the design but often limits future expandability. HBAs may support one, two or four ports using copper or optical fiber connectors. Typical Fibre Channel HBAs now employ 4 Gbit Fibre Channel ports but are easily backward compatible with slower 2 Gbit or 1 Gbit devices.
However, the selection of an HBA goes far beyond its installation and physical connectivity. Today's HBAs support vastly improved intelligence and data handling capabilities, often implementing proprietary techniques to improve data streaming or use alternate channels to maintain optimum data accessibility. Now that you've reviewed the essential issues involved in any SAN upgrade, this chapter covers the specific considerations for Fibre Channel HBAs. You'll also find a series of specifications to help make on-the-spot product comparisons between vendors, including Atto Technology Inc., Emulex and LSI Logic Corp.
Start with the vendor's recommendation. Industry experts point out that most Fibre Channel vendors will qualify HBAs and make HBA recommendations, so storage users often refer to the storage vendor's product compatibility matrix for HBA suggestions and any known caveats. It's usually a good idea to check compatibility matrices in order to screen out HBAs that are known to have compatibility problems or performance issues in your particular environment. If the compatibility matrix is unclear, the storage vendor can usually suggest one or more HBA products to evaluate.
Consider the host interconnects. The vast majority of HBA cards are compatible with PCI-X or PCIe (PCI Express) slots on the host server. Most HBA manufacturers offer both PCI-X and PCIe variants, so it's important to first identify the slot type and purchase the corresponding card model. For example, the Atto Celerity FC-42ES is made for PCIe, while the Celerity FC-42XS is built for PCI-X. Blade systems may require specialized HBAs. For example, Emulex provides a PCIe HBA for the Sun Blade 8000 Modular System, as well as Dell Inc., Hewlett-Packard Co. (HP) and IBM blade systems.
Consider the port speed and connectivity. Ports may support either optical cabling or copper cabling, but will not mix the two on one card. Be sure to select an HBA model with suitable connectors. Port speed is also important, and 4 Gbit Fibre Channel ports are now commonplace (10 Gbit Fibre Channel cards are slowly emerging). Experts recommend using 4 Gbit HBAs even if applications don't currently demand it -- this allows headroom for future bandwidth growth. Most 4 Gbit ports are fully backward compatible with slower 2 Gbit or even 1 Gbit Fibre Channel fabrics but it's important to verify backward compatibility before making a product choice.
Be sure to provide enough ports for key SAN features. Fibre Channel HBAs typically offer one, two or four ports. Additional HBAs would then be needed to supply additional ports. When considering an HBA purchase or upgrade, be sure to purchase enough ports to support storage area netword (SAN) features on each server, such as failover for resilient fabric accessibility. As another example, pairs of HBAs may be needed to improve performance and availability for server virtualization.
Evaluate the management tools. HBAs typically employ software tools for configuration and management. Consider the versatility and interoperability of the management tools. Tools that recognize and handle HBAs from various vendors anywhere across the fabric can be far more useful than specialized utilities that only work with a specific vendor's HBAs. For example, Emulex HBAs use HBAnyware software, while LSI Logic HBAs use MyStorage adapter management software.
Consider other specialized features. HBAs are incorporating increasingly more sophisticated features designed to improve data handling and availability. For example, the LSI Logic LSI7104XP-LC card improves performance using specialized internal processors to offload Fibre Channel tasks from the host system. Similarly, the Atto Celerity FC-44ES uses a proprietary technology dubbed Advanced Data Streaming (ADS) to accelerate data transfers and move large amounts of data more efficiently. Even the HBA itself may handle port virtualization. For example, the Emulex LPe11000 supports N_Port ID Virtualization (NPIV) and Virtual Fabric features. Weigh the effect of each feature on your storage infrastructure, but only invest in features that you intend to use.
The HBA specifications page in this chapter covers the following products:
- Atto Technology Inc.; Celerity FC-44ES HBA
- Atto Technology Inc.; Celerity FC-42ES HBA
- Emulex; LPe11002/LPe11000/LPe1150 PCI Express 4Gb/s HBAs
- LSI Logic Corp.; LSI7404XP-LC HBA
- LSI Logic Corp.; LSI7204XP-LC HBA
- LSI Logic Corp.; LSI7404EP-LC HBA
- LSI Logic Corp.; LSI7204EP-LC HBA
- QLogic Corp.; QLE2462/QLE2460 4Gbps FC HBAs
- QLogic Corp.; QLA2462/QLA2460 4Gbps FC HBAs