The trouble with measuring SAN performance


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Two ways to manage performance

AppIQ Manager: An application-integrated solution with optional add-ons that support Oracle and Exchange.

CreekPath Systems AIM Suite: Supports and integrates with a range of operating systems, Fibre Channel (FC) switches, HBAs and storage arrays.

EMC Control Center:

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Reports on and reactively responds to failed paths or performance hot spots. EMC is expanding this product to work with other storage arrays.

Precise Software i3 APM technology: Veritas recently acquired Precise Software's i3 APM technology that analyzes total system performance from the server and the application all the way down to the storage array level.

Other products: IBM/Tivoli SAN Manager, InterSAN Pathline, Storability Global Storage Manager and Veritas SANPoint Control provide varying levels of end-to-end performance monitoring and reporting.


HBAs: Emulex HBAnyware and QLogic SANblade Manager offer the ability to report and monitor performance on their HBAs, capturing such information as port status, throughput and problems the cards may experience

Switches: Brocade Fabric Manager, Cisco Fabric Manager, CNT/Inrange Enterprise Manager, McData SANavigator and QLogic SANblade Manager offer varying levels of abilities to display and capture performance statistics that measure port activity, utilization and throughput on their respective switches. For advanced FC performance analysis that works independently of the switch vendors, look to the Finisar GTX Analyzer.

Storage arrays: Most enterprise storage arrays vendors such as 3PAR, IBM, Network Appliance, StorageTek and Sun offer tools that minimally enable administrators to capture and report on various performance statistics. Some larger, monolithic storage arrays offer self-tuning performance tools such as EMC Symmetrix Optimizer and HDS HiCommand Tuning Manager that respond to hot spots on disk drives and can dynamically move data within the array to alleviate this contention.

Servers/operating systems: Demand Technology NTSMF, Fujitsu Softek Server Manager and NetScout Systems NetScout Server are just a few in a long list of the performance management tools that compliment the utilities included in most operating systems today.

The agent problem
It's ironic, but performance-tuning software can create its own set of performance problems. As performance agents scamper from component to component, they clog the storage environment.

For this reason, Peter Galvin, CTO, Corporate Technologies says his company stopped selling and supporting such a product. When deployed, this product's agent consumed 10% of the server's CPU and generated additional network traffic.

Chris Gahagan, EMC's senior VP of infrastructure software, says that administrators should expect agents to consume no more than 1% to 2% of CPU and memory overhead. Any more than that, and the agent becomes obnoxious. He believes that to keep performance management agents at that level, they should only focus on gathering and monitoring high-level data. They should only consume more resources when they start to spot a problem thereby requiring more options to be turned on. However, once the problem is identified and solved, the agent should automatically throttle back to its default configuration.

Another problem is simply getting the agents on the servers, configuring them and maintaining them once they are there. Installing and configuring agents on 10 or 20 servers running Windows is one level of difficulty. Doing the same thing on a couple hundred servers with different operating systems and databases creates a whole new level of complexity. The good news is that there's progress to report on this front. EMC's Gahagan believes software agents should be self- propagating and distribute themselves to the servers running them. EMC is currently building an agent architecture that uses a distribution server to propagate agents to the servers it supports.

AppIQ hopes to minimize or avoid the whole agent issue by programming their central server to open a connection to either Microsoft's Windows Management Instrumentation (WMI) interface or the various Unix vendors' versions of it. Sun Solaris has had this functionality since Solaris 7, while IBM is currently preparing a version of it for their releases of Linux and AIX. Buyer beware: Many of these products are still in early stages of release.

Best bets for now
An administrator pondering what approaches to take for their performance-management needs should probably use a combination of point solutions in heterogeneous environments or tools from storage array vendors in homogeneous storage networks. Too many of today's tools designed for heterogeneous environments are either still in their infancy, are dying on the vine such as BMC's Storage Patrol, or only work in qualified heterogeneous environments where it works with a limited number of storage arrays and operating systems such as CreekPath Management Suite.

Of the point solutions that only get information from one operating system, database, switch or storage array, your time would be better spent tuning these applications, understanding them and getting them synced up in your environment than looking to any third-party tool. Performance management software will continue to be more of an exercise in brute force than an art form for the foreseeable future. Emerging standards, questions about functionality, tight budgets and the fact that measuring SAN performance is not a priority in most environments until something goes wrong will contribute to an overall procrastination in deploying this technology.

This was first published in October 2003

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