> # Information About Performance Manager

> This section includes the following topics:

> - Data Interpolation
> - Data Collection
> - Using Performance Thresholds
> - Creating a Flow Using Performance Manager Flow Wizard

> Performance Manager gathers network device statistics historically and provides this information graphically using a web browser. It presents recent statistics in detail and older statistics in summary. Performance Manager also integrates with external tools such as Cisco Traffic Analyzer.

> The Performance Manager has three operational stages:

> - Definition—The Flow Wizard sets up flows in the switches.
> - Collection—The Web Server Performance Collection screen collects information on desired fabrics.
> - Presentation—Generates web pages to present the collected data through DCNM-SAN Web Server.

> Performance Manager can collect statistics for ISLs, hosts, storage elements, and configured flows. Flows are defined based on a host-to-storage (or storage-to-host) link. Performance Manager gathers statistics from across the fabric based on collection configuration files. These files determine which SAN elements and SAN links Performance Manager gathers statistics for. Based on this configuration, Performance Manager communicates with the appropriate devices (switches, hosts, or storage elements) and collects the appropriate information at fixed five-minute intervals.

> Performance Manager uses a round-robin database to hold the statistical data collected from the fabric. This data is stored based on the configured parameters in the collection configuration file. At each polling interval, Performance Manager gathers the relevant statistics and stores them in the round-robin database. This database is a fixed size and will not grow beyond its preset limits.

> Performance Manager creates a series of archived data to hold summarized information present in the real-time round-robin database. This archived data is used to generate daily, weekly, monthly, and yearly consolidated reports. In this way, Performance Manager maintains significant historical data without the cost of an ever-increasing database size.

> Note You must restart Performance Manager if you change the user credentials on DCNM-SAN Server.

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