Hosts
A host system is a computer that is connected to the system through one of the following: a Fibre Channel interface, serial-attached SCSI (SAS) connections, or an IP network. To use Fibre Channel or Fibre Channel over Ethernet connections to a storage area network (SAN), an optional host interface adapter must be installed.
The SAS host ports on Storwize® V5000 Gen2 node canisters can operate at 6 Gbps or 12 Gbps. The Storwize V5020 system has two onboard 12 Gbps host attachment SAS ports. Storwize V5020 systems can also support the optional SAS host interface adapter. Storwize V5010 and Storwize V5030 systems support 12 Gbps SAS host attachment I/O but must have the optional host interface adapter installed. These models require different cables based on the speeds. If you want to run 12 Gbps SAS, you need to use a 12 Gbps cable.
A host object is a logical object that represents a list of worldwide port names (WWPNs) and a list of iSCSI names that identify the interfaces that the host system uses to communicate with the system. Both Fibre Channel and SAS connections use WWPNs to identify the host interfaces to the systems. iSCSI names can be either iSCSI qualified names (IQNs) or extended unique identifiers (EUIs).
A typical configuration has one host object for each host system that is attached to the system. If a cluster of hosts accesses the same storage, you can add host bus adapter (HBA) ports from several hosts to one host object to make a simpler configuration. A host object can have both WWPNs and iSCSI names.
The system does not automatically present volumes to the host system. You must map each volume to a particular host object to enable the volume to be accessed through the WWPNs or iSCSI names that are associated with the host object. For Fibre Channel and SAS-attached hosts, the system reports the node login count, which is the number of nodes that can detect each WWPN. If the count is less than expected for the current configuration, you might have a connectivity problem. For iSCSI-attached hosts, the number of logged-in nodes refers to iSCSI sessions that are created between hosts and nodes, and might be greater than the current number of nodes on the system.
When you create a new Fibre Channel host object, the system presents a list of candidate WWPNs that have logged into the system but are not yet configured in host objects. Some Fibre Channel HBA device drivers do not leave their ports logged in if no disks are detected on the fabric, so they are not visible in the list of candidate ports. You must enter the WWPNs for such hosts manually. There is no equivalent list of candidate IQNs available when creating iSCSI hosts. All iSCSI host port IQNs must be entered manually.
The system can detect only WWPNs that have connected to the system through the Fibre Channel network, SAS network, or through any IP network. Some Fibre Channel HBA device drivers do not leave ports logged in if no disks are detected on the fabric or IP network. The system can detect only WWPNs that have connected to the system through the Fibre Channel network or through any IP network. Some Fibre Channel HBA device drivers do not leave ports logged in if no disks are detected on the fabric or IP network. The configuration interface provides a method to manually type the port names. There is no equivalent list of candidate IQNs available when creating iSCSI hosts. All iSCSI host port IQNs must be entered manually.
A WWPN or iSCSI name can be added to only one host object.