text: **3.13 Host mapping and LUN masking**
  
  Host mapping is similar in concept to LUN mapping or masking. LUN mapping is the process 
  of controlling which hosts have access to specific LUs within the disk controllers. LUN 
  mapping is typically done at the storage system level. Host mapping is done at the software 
  level. 
  
  LUN masking is usually implemented in the device driver software on each host. The host has 
  visibility of more LUNs than it is intended to use. The device driver software masks the LUNs 
  that are not to be used by this host. After the masking is complete, only some disks are visible 
  to the operating system. The system can support this type of configuration by mapping all 
  volumes to every host object and by using operating system-specific LUN masking 
  technology. However, the default (and preferred) system behavior is to map only those 
  volumes that the host is required to access. 
  
  The act of mapping a volume to a host makes the volume accessible to the WWPNs or iSCSI 
  names such as iSCSI qualified names (IQNs) or extended-unique identifiers (EUIs) that are 
  configured in the host object. 
  
  **3.13.1 Planning for large deployments**
  
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              [html]<thead><tr><td>group to single I / O Group only. This epproach allows you to configure up to 2048 host objects on a system with four I / O Groups ( eight nodes ).</td></tr></thead><tbody><tr><td>For best performance, split each host group into two sets. For each set, configure the preferred access node for volumes presented to the host set to one of the I / Oroup nodes.</td></tr><tr></tr><tr></tr></tbody>
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  **71** Chapter 3. Planning 