The tempdb is a temporary work space for the Microsoft SQL Server itself. The tempdb is recreated every time the Microsoft SQL Server instance is started, so the system always starts with a clean copy of the database. There is never any data in tempdb that should be saved from one session of Microsoft SQL Server to another, so there is no need to include tempdb in a virtual machine level backup, or to replicate tempdb in a multisite disaster recovery solution. Consider placing tempdb on its own dedicated VMDK to exclude it from any unnecessary operations.

When deploying AlwaysOn Availability Groups with a readable secondary replica, consider that tempdb space will increase due to the following:

Tempdb is a Microsoft SQL Server instance level resource. If you configure multiple databases in a single failover solution, the capacity of the tempdb must be able to accommodate demands from the aggregate of databases.