Per the IT Analytics (ITA) Server Administrator Guide, the sysadmin SQL Server role must be assigned to the ITA service account that will be assigned to the ITA application pool in IIS during installation:

[The] service account will become the identity of the application pool used by the IT Analytics Server; therefore it is also the IT Analytics Server identity. At runtime this service account will require the following permissions:

• Administrator rights to the SQL Server Database Engine instance hosting the IT Analytics SQL database (granted automatically by the setup program).
• Administrator rights to the SQL Analysis Services server instance hosting the OLAP cube database.
• Administrator rights to the SQL Server Agent instance hosting the IT Analytics processing jobs.
• Administrator rights to the SQL Server Reporting Services report manager website.

Can the sysadmin SQL role be removed from the ITA service account post-installation?

Version: 2.9.1

Component: ITAnalyticsAppPool

The sysadmin role is required for creating, modifying, and deleting SQL Server Agent jobs. Within the context of IT Analytics, the ITA application pool identity must be assigned the sysadmin role in SQL Server in order to create, modify, and delete jobs used to process the IT Analytics cubes.