6.5.1

Host-based iSCSI initiators establish connections to each target. Storage systems with a single target
containing multiple LUNs have traffic to all the LUNs on a single connection. With a system that has three
targets with one LUN each, a host uses separate connections to the three LUNs. This information is
useful when you are trying to aggregate storage traffic on multiple connections from the host with multiple
iSCSI HBAs, where traffic for one target can be set to a particular HBA, while traffic for another target can
use a different HBA.
iSCSI Storage System Types
ESXi supports different storage systems and arrays.
The types of storage that your host supports include active-active, active-passive, and ALUA-compliant.
Active-active storage
system
Supports access to the LUNs simultaneously through all the storage ports
that are available without significant performance degradation. All the paths
are always active, unless a path fails.
Active-passive storage
system
A system in which one storage processor is actively providing access to a
given LUN. The other processors act as a backup for the LUN and can be
actively providing access to other LUN I/O. I/O can be successfully sent
only to an active port for a given LUN. If access through the active storage
port fails, one of the passive storage processors can be activated by the
servers accessing it.
Asymmetrical storage
system
Supports Asymmetric Logical Unit Access (ALUA). ALUA-compliant storage
systems provide different levels of access per port. With ALUA, hosts can
determine the states of target ports and prioritize paths. The host uses
some of the active paths as primary and others as secondary.
Virtual port storage
system
Supports access to all available LUNs through a single virtual port. Virtual
port storage systems are active-active storage devices, but hide their
multiple connections though a single port. ESXi multipathing does not make
multiple connections from a specific port to the storage by default. Some
storage vendors supply session managers to establish and manage
multiple connections to their storage. These storage systems handle port
failovers and connection balancing transparently. This capability is often
called transparent failover.
Discovery, Authentication, and Access Control
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.
vSphere Storage
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