Which module in OpenStack provides persistent block storage?

The module in OpenStack that provides persistent block storage is Cinder. Cinder is specifically designed to manage block storage devices and allows users to create, attach, and manage persistent volumes that can be used by instances running in the OpenStack environment. This capability is crucial for applications that require reliable and durable storage that can persist beyond the life cycle of a particular compute instance.

Cinder supports various back-end storage solutions, allowing users to choose different storage technologies to meet their performance and durability requirements. This is essential for workloads that demand high availability and data resilience, as it enables users to connect their compute resources to storage that can be scaled independently.

In contrast, the other options represent different functionalities within the OpenStack architecture. Swift is utilized for object storage, which is suited for storing unstructured data like images and multimedia files rather than block storage. Glance serves as the image service for storing and retrieving virtual machine images; it does not handle block storage directly. Nova manages compute resources and orchestrates the lifecycle of instances but does not provide storage solutions itself. Therefore, Cinder is the correct answer as it directly addresses the need for persistent block storage in an OpenStack environment.