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Disaster Recovery Scenarios and Strategies

There are many ways to implement a disaster recovery solution for CALUMO.  In this article we will look at two of them, machine failure and site failure.

This is for CALUMO on premises installations only.

Machine Failure

This style of disaster recovery aims to allow the system to continue to function in the case of a machine level failure such as a failure of a HDD.

In this instance, you should configure your server environment as follows

Web Servers

Two or more machines should be setup as an IIS web farm using the following detailed documentation from Microsoft: 

Once that is completed, you will need to install CALUMO on one of the web servers with the following amendments to the installation process:

  • For the installation path, specify the UNC path to a location that is on the highly available file server that all Web Server machines can access

SQL Servers

Two or more machines should be set up as a SQL Server, highly available cluster using the detailed documentation from Microsoft:

Once the cluster is configured, reconfigure your CALUMO Web application to point to the load balanced DNS of the cluster for its connection strings and Analysis Services mappings.

Site Failure

This style of disaster recovery aims to allow the system to continue to function in the case of a site wide outage such as power failure or natural disaster. In this instance, you should configure your server environment as follows:

Web Servers

This scenario is about setting up a replication of configuration and application files from your primary site to a secondary site.  You will need to:

  • Create a directory on your web server that will be replicated, say C:\Replicated\
  • Configure the primary web server to run IIS in shared configuration mode and point it to use a sub folder of the replicated folder, e.g. C:\Replicated\IISConfig
  • Install the CALUMO Web server into a sub-folder of the replicated folder eg C:\Replicated\CALUMO
  • Build and configure an identical IIS server in your secondary site
  • Configure DFS to replicate the folder to the same location: Step-by-Step Guide to Distributed File System (Dfs)
  • Configure IIS in the secondary site to run shared configuration off the replicated folder

The default delay in DFS replication is 15 minutes, which should be ample as the files on the disk in the CALUMO application only change when there is an upgrade.

SQL Servers

This scenario will be about having fairly close to real time data mirroring using the SQL Server Log Shipping feature.

Microsoft have detailed documentation about how to configure your environment for log shipping: