Binary Storage Configuration

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This topic describes how DevExpress ASPxCapcha, WebChartControl, ASPxGauges and ASPxBinaryImage controls support the IIS clustered web environment (also known as a Web Farm or a Web Garden).

A Web Farm hosts a web application on multiple web servers, whereas a Web Garden runs an application on the same server - but in different worker processes. In a Web Garden, each worker process is executed on its own processor - specified by the Internet Information Services (IIS) settings of the server host where the application is deployed.

A Web Garden specifies multiple worker processes for an application pool that yields the following advantages.

  • Robust request processing: when a worker process in an application pool is busy (e.g., when a script engine stops responding), other worker processes can accept and process requests for the application pool.
  • Reduced resource competition: when a Web Garden reaches a steady state, each new TCP/IP connection is assigned to a worker process (within the Web Garden) based on a round-robin load distribution. This balances workloads and reduces competition for resources that are bound to a worker process.

Under default settings, a binary storage mechanism does not work with Web Farms or Web Gardens for enhanced binary image transformation from a specified binary storage to the client.

To utilize Web Farms and Web Gardens, use the control's BinaryStorageMode property (ASPxBinaryImage.BinaryStorageMode, ASPxGaugeControl.BinaryStorageMode, CaptchaImageProperties.BinaryStorageMode, WebChartControl.BinaryStorageMode), the BinaryStorageConfigurator.Mode field, and BinaryStorageConfigurator.RegisterCustomStorageStrategy and BinaryStorageConfigurator.RegisterStorageStrategy methods to modify binary storage settings.

The BinaryStorageMode property provides the following modes.

Value Description
Default Uses the Cache mode if a configuration is not defined by the BinaryStorageConfigurator.Mode field.
Session Stores binary data within a session. Web Gardens and Web Farms can be used by the binary storage mechanism if an application session is configured with the SQL Server or State Server Session-State Mode.
Cache Binary data is stored within a cache. Web Gardens and Web Farms will not work correctly in this mode.
Custom Custom mode provides for implementing a custom scenario for storing and accessing binary data. Web Farms and Web Gardens should work if the custom configuration implements storing the binary data on the hard drive, or by using a web service. For more details, use the How to Define Custom Binary Storage Configuration Code Central example, which implements storing binary images on a hard drive.
NOTE

To specify the binary storage mode for DevExpress ASPxCapcha, ASPxCharts, ASPxGauges and ASPxBinaryImage controls simultaneously, define the BinaryStorageMode property within the global.asax file as shown below:

void Application_Start(object sender, EventArgs e) { DevExpress.Web.BinaryStorageConfigurator.Mode = DevExpress.Web.BinaryStorageMode.Session; }