During planning, with the SME's help, you should review each application and record the following:
■ The location of the installation media. Often, the SME is the best source of information about the location of the source media, such as CDs, disks, and so on.
■ Settings that differ from the application's default settings that are required to deploy the application in a desired configuration .
■ External connections . For example, does the application require a connection to a database, mainframe, Web site, or other application server?
■ Constraints associated with the application.
■ Deployment compatibility. Is the application compatible with disk imaging and Sysprep? Is the application compatible with 32-bit systems? 64-bit systems?
■ Application dependencies. Does the application depend on any patches or other applications?
Most companies share a common goal: create a corporate-standard desktop configuration based on a common image for each operating system version . They want to apply a common image to any desktop in any region at any time and then customize that image quickly to provide services to users
In reality, most organizations build and maintain many images—sometimes even hundreds of images . By making technical and support compromises and disciplined hardware purchases, and by using advanced scripting techniques, some organizations have reduced the number of images they maintain to between one and three . These organizations tend to have the sophisticated software distribution infrastructures necessary to deploy applications— often before first use—and keep them updated.
Business requirements usually drive the need to reduce the number of images that an organization maintains. Of course, the primary business requirement is to reduce ownership costs . The following list describes costs associated with building, maintaining, and deploying disk images:
■ Development costs Development costs include creating a well-engineered image to lower future support costs and improve security and reliability. They also include creating a predictable work environment for maximum productivity balanced with flexibility. Higher levels of automation lower development costs .
■ Test costs Test costs include testing time and labor costs for the standard image, the applications that might reside inside it, and those applications applied after deployment. Test costs also include the development time required to stabilize disk images .
■ Storage costs Storage costs include storage of the deployment shares, disk images, migration data, and backup images Storage costs can be significant, depending on the number of disk images, number of computers in each deployment run, and so on
■ Network costs Network costs include moving disk images to deployment shares and to desktops
As the size of image files increases, costs increase Large images have more updating, testing, distribution, network, and storage costs associated with them. Even though you update only a small portion of the image, you must distribute the entire file .
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