Maximum SAN performance requires key components--host bus adapters and Fibre Channel directors--to work in harmony.

SANs are among the most mission-critical enterprise networks, so organizations tend to overbuy and overallocate SAN capacity to avert performance problems. Buying more capacity might work sometimes, but it isn't always an option. Storage administrators need to find ways to wring more value out of their SANs, and performance tuning is the place to start.

				SAN tuning checklist
				Use this checklist as a guide for performance tuning. Host bus adapters (HBAs) Leave the Fibre Channel (FC) ports at autonegotiate Avoid putting more HBAs on a server than the bus throughput can support Turn on the I/O coalesce parameter in high-performance environments Install the latest HBA firmware and driver Use multipathing software that supports both load balancing and path failover FC switches Keep the highest performing directors at the core of the SAN Connect storage devices and the highest performing applications to the core Benchmark the performance on oversubscribed ports Leave the FC ports at autonegotiate for host and storage connections

All SAN hardware vendors offer tools that configure, monitor and collect performance data for their devices. For example, Emulex Corp.'s HBAnyware allows administrators to discover host bus adapters (HBAs) and collect data about their status, attributes and performance. Brocade Communications Systems Inc.'s optional Advanced Performance Monitoring tool collects SilkWorm director performance data, which can be viewed in its Fabric Manager or exported to Microsoft Excel. EMC Corp.'s Navisphere Analyzer, an add-on to its Navisphere Management Suite, allows Clariion users to gather performance data and identify trends. Yet the key to SAN performance tuning is knowing what device settings to monitor--for HBAs, Fibre Channel (FC) directors, arrays or tape libraries--and when their parameters need adjusting (see "SAN tuning checklist").

FC HBAs
Appropriately configuring an HBA before it's connected to the SAN is the best way to ensure that the HBA isn't the source of a SAN performance problem. Initial considerations when selecting and configuring an HBA include:

• Number of HBA ports
• Number of HBAs on the server
• Placement of HBAs on the server
• What load-balancing and path failover software to use
• Version and type of HBA driver and firmware
• Internal HBA settings