text: **Grain**
  A grain is the unit of data that is represented by a single bit in a FlashCopy bitmap (64 KiB or 
  256 KiB) in the IBM Storwize V7000. A grain is also the unit to extend the real size of a 
  thin-provisioned volume (32 KiB, 64 KiB, 128 KiB, or 256 KiB). 
  
  **Hop**
  One segment of a transmission path between adjacent nodes in a routed network. 
  
  **Host bus adapter**
  A host bus adapter (HBA) is an interface card that connects a server to the SAN environment 
  through its internal bus system, for example, PCI Express. Typically it is referred to the Fibre 
  Channel adapters. 
  
  **Host ID**
  A host ID is a numeric identifier that is assigned to a group of host FC ports or internet Small 
  Computer System Interface (iSCSI) host names for LUN mapping. For each host ID, SCSI IDs 
  are mapped to volumes separately. The intent is to have a one-to-one relationship between 
  hosts and host IDs, although this relationship cannot be policed. 
  
  **Host mapping**
  Host mapping refers to the process of controlling which hosts have access to specific 
  volumes within a cluster. Host mapping is equivalent to LUN masking. 