The LifeKeeper IIS Recovery continuously monitors the health of Internet servers, and if a problem arises, provides automatic failover of the affected web service to a standby system. The Recovery Kit protects Web, FTP and SMTP services of the Microsoft Internet Information Server (IIS), Multiple Web, FTP or SMTP sites can be stopped/started independently.
The IIS Recovery Kit protects Internet servers from the following problems:
- System failure or server shutdown
- Network Interface Card (NIC) failures
- Communication failures (Web server is running but stops responding)
- Startup failures (Web server aborts on startup)
LifeKeeper can be configured to run in an Active/Active (or Active/Backup) configuration. The image below illustrates an Active/Active environment, where each server, under normal circumstances, is active - but also acts as a backup to another. This approach allows for maximum hardware utilisation, and removes the need for a rack of machines which are essentially sitting idle.
Cluster Configurations
As well as the Active/Active configuration it is possible to have an N+1 configuration, where N machines are active, and 1 machine acts as a standby to all of them. This allows for better performance in the event of a single failover, as a single machine will not be doing the job of two.
Data Replication
LifeKeeper also provides a mirroring product (Extended Replication) which is capable of mirroring data either locally over a LAN or to remote sites over a WAN. Mirroring of data over a WAN allows for a true disaster recovery approach, and helps ensure that in the event of a failure within one geographic area, service will move to the remote site (which contains an up to date copy of the data).
The data replication software can also be used on a local environment to remove the requirement for an expensive shared storage solution. This allows for a reduced cost solution, while still giving the benefits of data availability. This type of configuration allows for a lower cost entry point into high availability solutions, and allows the cluster to scale with demand in the future. However, the mirroring of data for any one application can only take place across two nodes.
Recovery scenario of IIS
The IIS Recovery Kit has two recovery procedures. For system or NIC failures, the Recovery Kit transfers the affected web server’s resources to a standby system, and then starts up the standby web server. If there is a communications or startup failure, and local recovery is enabled, the IIS Recovery Kit will first stop and restart the affected web server to see if that corrects the problem. If the restart is unsuccessful, then the Recovery Kit transfers service to the backup web server.
The IIS Recovery Kit manages the dependencies between the IIS application, IP and volume resources.
Configuration and setup of an IIS server under LifeKeepers control is a relatively straight forward process, and supports virtual hosting if required.
First, you create the IP and volume resources to be used by your web servers. Then, when you create the IIS resource, the IIS Recovery Kit reads the Microsoft IIS configuration and automatically creates the required dependencies between the IIS resource and the IP and volume resources.
The following is a sample IIS hierarchy as shown in the LifeKeeper GUI. The Web site has a dependencies on both the IP address “Switchable118”, and on the volume “WEB.Vol.G”, where the home directory containing the Web site’s content resides. Both the IP and volume resources were created prior to the web site creation.
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 Web site,
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 Server 2 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 assume service. 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 IIS Recovery Kit allows you to manually switch service back or take advantage of the LifeKeeper automatic switchback feature.
