You can use several mechanisms to discover your storage and to limit access to it.
You must configure your host and the iSCSI storage system to support your storage access control policy.
A discovery session is part of the iSCSI protocol, and it returns the set of targets you can access on an iSCSI storage system. The two types of discovery available on ESXi are dynamic and static. Dynamic discovery obtains a list of accessible targets from the iSCSI storage system, while static discovery can only try to access one particular target by target name and address.
For more information, see Configuring Discovery Addresses for iSCSI Adapters.
iSCSI storage systems authenticate an initiator by a name and key pair. ESXi supports the CHAP protocol, which VMware recommends for your SAN implementation. To use CHAP authentication, the ESXi host and the iSCSI storage system must have CHAP enabled and have common credentials.
For information on enabling CHAP, see Configuring CHAP Parameters for iSCSI Adapters.
Access control is a policy set up on the iSCSI storage system. Most implementations support one or more of three types of access control:
By initiator name
By IP address
By the CHAP protocol
Only initiators that meet all rules can access the iSCSI volume.
Using only CHAP for access control can slow down rescans because the ESXi host can discover all targets, but then fails at the authentication step. iSCSI rescans work faster if the host discovers only the targets it can authenticate.