To communicate with each other, iSCSI initiators and targets establish iSCSI sessions. You can review and manage iSCSI sessions using vSphere CLI.
By default, software iSCSI and dependent hardware iSCSI initiators start one iSCSI session between each initiator port and each target port. If your iSCSI initiator or target have more than one port, your host can have multiple sessions established. The default number of sessions for each target equals the number of ports on the iSCSI adapter times the number of target ports.
Using vSphere CLI, you can display all current sessions to analyze and debug them. To create more paths to storage systems, you can increase the default number of sessions by duplicating existing sessions between the iSCSI adapter and target ports.
You can also establish a session to a specific target port. This can be useful if your host connects to a single-port storage system that, by default, presents only one target port to your initiator, but can redirect additional sessions to a different target port. Establishing a new session between your iSCSI initiator and another target port creates an additional path to the storage system.
The following considerations apply to iSCSI session management:
Some storage systems do not support multiple sessions from the same initiator name or endpoint. Attempts to create multiple sessions to such targets can result in unpredictable behavior of your iSCSI environment.
Storage vendors can provide automatic session managers. Using the automatic session manages to add or delete sessions, does not guarantee lasting results and can interfere with the storage performance.