The correct utility to join stateless ESXi hosts to an Active Directory domain is the vSphere Authentication Proxy. The vSphere Authentication Proxy allows hosts to be authenticated with Active Directory without requiring each host to store the AD credentials. This enhances security, especially for stateless hosts which could otherwise have issues storing persistent configuration data.
To move a group of VMs to another port group, a vSphere administrator can use vSphere vMotion. vSphere vMotion allows for live migration of running virtual machines from one host to another without downtime. This includes moving VMs across different networks or port groups while maintaining network connections and service continuity.
To secure iSCSI devices in a vSphere environment, it is important to ensure that ESXi hosts authenticate to the target. Authentication helps to prevent unauthorized access to the iSCSI target and ensures only legitimate ESXi hosts can connect, thereby providing a secure communication channel.
VM snapshots should be checked to address immediate performance concerns. Snapshots can negatively affect the performance of a virtual machine based on how long they have been in place, their depth, and the changes made to the VM and its guest operating system since the snapshot was taken. It is important not to run production VMs from snapshots on a permanent basis, as this can lead to performance degradation.