Configuration Definitions and Restrictions

Active/Active Configuration

IIS allows multiple Web and FTP sites and SMTP virtual servers to run on each server in a cluster. Only a single instance of the IIS software is allowed (or required) on a given system. The Web sites, FTP sites and SMTP virtual servers can be protected and managed individually by LifeKeeper. Subsequent descriptions may use the term “site” to refer generically to a Website, FTP site or SMTP virtual server.

The figure below illustrates a typical configuration of web servers.

In this configuration, each server has two Web sites: one primary and one backup Web site. Server 1 has the primary instance of WebSite1 and the backup instance of WebSite2. Server 2 has the reciprocal configuration: a primary instance of WebSite2 and a backup instance of WebSite1. Only the primary instances of the Web sites actually service incoming user requests on any given server.

In addition, Server 1 has the primary instance of an FTP site named FTPsite and the backup instance of the SMTP virtual server named SMTPvs, while Server2 has the backup instance of the FTP site and the primary instance of the SMTP virtual server.

If a primary Web site stops servicing user requests, LifeKeeper activates the backup instance on the backup server to resume service there. Thus, if WebSite1 on Server 1 fails, then LifeKeeper activates the backup instance of WebSite1 on Server 2. After the switchover, there will be two active instances running on Server 2. Once the problem with the failed web server is corrected,you may switch service back to Server 1. The LifeKeeper Microsoft IIS Recovery Kit allows you to manually switch service back or take advantage of the LifeKeeper automatic switchback feature.