
Mastering Ansible, 4th Edition
By :

An alternative to the in-place upgrade strategy is the expand and contract strategy. This strategy has become popular of late, thanks to the self-service nature of on-demand infrastructures, such as cloud computing or virtualization pools. The ability to create new servers on-demand from a large pool of available resources means that every deployment of an application can happen on brand new systems. This strategy avoids a host of issues, such as a buildup of cruft on long-running systems, such as the following:
Starting fresh each time also removes the differences between initial deployment and an upgrade. The same code path can be used, reducing the risk of surprises when upgrading an application...