8.2 Host clusters 8.3 N-Port Virtualization ID support 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 PowerHAfi, and  Microsoft Cluster Server (MSCS). The following new commands were added to deal with host clusters: 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. 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. The usage model for the Storwize V7000 is based on a two-way active/active node model.  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. Chapter 8. Hosts  319 GLYPH<SM590000> rmvolumehostclustermap GLYPH<SM590000> rmhostcluster GLYPH<SM590000> rmhostclustermember GLYPH<SM590000> mkhost  (modified to put host in a host cluster on creation) GLYPH<SM590000> lshostclustervolumemap GLYPH<SM590000> lshostclustermember GLYPH<SM590000> lshostcluster