Chapter 8. Hosts 319
8.2  Host clusters
IBM Storwize V7000 software supports host clusters starting with V7.7.1 and later. The host 
cluster allows a user to create a group of hosts to form a cluster. A cluster is treated as a 
single entity, which allows multiple hosts to access the same volumes. 
Volumes that are mapped to a host cluster are assigned to all members of the host cluster 
with the same SCSI ID. 
A typical user case is to define a host cluster that contains all of the WWPNs belonging to the 
hosts participating in a host operating system-based cluster, such as IBM PowerHA®, and 
Microsoft Cluster Server (MSCS).
The following new commands were added to deal with host clusters:
/SM590000lshostcluster
/SM590000lshostclustermember
/SM590000lshostclustervolumemap
/SM590000mkhost (modified to put host in a host cluster on creation)
/SM590000rmhostclustermember
/SM590000rmhostcluster
/SM590000rmvolumehostclustermap
8.3  N-Port Virtualization ID support
The usage model for the Storwize V7000 is based on a two-way active/active node model. 
This is a pair of distinct control modules that share active/active access for any specific 
volume. These nodes each have their own Fibre Channel worldwide node name (WWNN). 
Therefore, ports that are presented from each node have a set of worldwide port names 
(WWPNs) that are presented to the fabric.
Traditionally, if one node fails or is removed for some reason, the paths that are presented for 
volumes from that node go offline. In this case, it is up to the native O/S multipathing software 
to fail over from using both sets of WWPN to only those that remain online. Although this 
process is what multipathing software is designed to do, occasionally it can be problematic, 
particularly if paths are not seen as coming back online for some reason. 
Starting with Storwize V7000 V7.7, the system can be enabled into N_Port ID Virtualization 
(NPIV) mode. When NPIV mode is enabled on the Storwize V7000 system, ports do not 
come online until they are ready to service I/O, which improves host behavior around node 
unpends. In addition, path failures because of an offline node are masked from hosts and 
their multipathing driver do not need to perform any path recovery. 
When NPIV is enabled on Storwize V7000 nodes, each physical WWPN reports up to four 
virtual WWPNs, as listed in Table 8-1.
Table 8-1   IBM Spectrum Virtualize NPIV Ports
NPIV port Port description
Primary Port This is the WWPN that communicates with backend storage and can 
be used for node to node traffic (local or remote).
Primary scsi Host Attach 
Port
This is the WWPN that communicates with hosts. It is a target port 
only. This is the primary port, so it is based on this local node’s 
WWNN.