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SANs are among the most mission-critical enterprise networks, so organizations tend to overbuy and over-allocate 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.
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 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.
Use this checklist as a guide for performance tuning:
- Leave the 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
- 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
Of course, SAN tuning is a work in progress. You need to constantly monitor and tinker with your storage fabric on a regular basis to get the best performance. By taking simple steps to tune SAN components before they're installed in the SAN, and knowing which ones to analyze first when performance hiccups occur, the number of performance issues will be greatly reduced down the road.
Do you know…
How to use a director switch?
Jerome M. Wendt is a storage analyst specializing in open-systems storage and SANs. Systems engineer Mike Skomal also contributed to this article.
This was first published in June 2006