File shares are handled differently between the Shared File Systems service (manila), Ceph File System (CephFS), and CephFS through NFS.
The Shared File Systems service provides shares, where a share is an individual file system namespace and a unit of storage with a defined size. Shared file system storage inherently allows multiple clients to connect, read, and write data to any given share, but you must give each client access to the share through the Shared File Systems service access control APIs before they can connect.
With CephFS, a share is considered a directory with a defined quota and a layout that points to a particular storage pool or namespace. CephFS quotas limit the size of a directory to the size share that the Shared File Systems service creates. Access to Ceph shares is determined by MDS authentication capabilities.
With native CephFS, file shares are provisioned and accessed through the CephFS protocol. Access control is performed with a CephX authentication scheme that uses CephFS usernames.