One of the most important components is the Citrix Data Store. The Datastore is a database storing the static information about the Citrix Farm. Think of settings for the load evaluator, published applications, zones and much more.

When writing a design the decisions made for the Data Store can have much influence in the practical usage of the Citrix infrastructure.

• Type of Database

First the type of database you would like to use should be determined. Citrix supports several databases like MS Access, MS SQL Express, MS SQL, IBM DB2 and Oracle. The MS Access database and MS SQL Express database will be hosted on the first server on which Citrix XenApp will be installed, while MS SQL, IBM DB2 and Oracle databases normally or hosted on a dedicated database server.

• Direct or Indirect Mode

During the installation of Citrix XenApp you will be asked of the database will be accessed direct or indirect by the server. MS Access and SQL Express databases can only be accessed indirectly where you have the option when using MS SQL, IBM DB2 or Oracle. When using the indirect mode the server will ask one server to access the datastore for the requested information. In other words there is Single Point of Contact accessing the database.

• Reliability

When writing a design also the reliability of the database is important. Although the server can perform their tasks for a while without a database connection, no changes can be made to the configuration of the Citrix Farm. Try to determine the amount of changes to the farm and the importance/priority of those changes in the case the database is unavailable. For such situations on a database level several options are available to create a redundancy using replications, clustered database or similar solutions.

• Bandwidth (Replication of Databases)

When the servers are divided geographically over low bandwidth lines it can be good idea to choose for database replication, so every location has a copy of the datastore available locally. Remember that (a bit depend on the type of database) this creates more complexity for the environment and also database replication uses bandwidth.