HP 3PAR StoreServ 7200 2-node HP 3PAR SmartStart 1.1.1 User's Guide ( - Page 38

Each layer is created from elements of the layer above: • Chunklets are drawn from physical disks. • Logical disks are created from groups of chunklets. • Common Provisioning Groups (CPGs) are groups of logical disks. • Virtual volumes use storage space provided by CPGs. Physical Disks A physical disk is a disk drive mounted on a drive magazine located in drive cages (or drive enclosures) in an HP 3PAR storage system. Chunklets Physical disks are divided into chunklets. Each chunklet occupies contiguous space on a physical disk. On HP 3PAR StoreServ 7000 Storage systems, all chunklets are 1 GB. Chunklets are automatically created by the HP 3PAR Operating System, and they are used to create logical disks. A chunklet is assigned to only one logical disk. RAID and Logical Disks A logical disk is a collection of physical disk chunklets arranged as rows of RAID sets. Each RAID set is made up of chunklets from different physical disks. Logical disks are pooled together in Common Provisioning Groups (CPGs), which allocate space to virtual volumes. The underlying logical disks are automatically created by the HP 3PAR OS when you create CPGs. NOTE: Logical disks are an advanced storage component. For more information, see the HP 3PAR Management Console User Guide or the HP 3PAR StoreServ Storage Concepts Guide. To access these documents, go to the HP 3PAR StoreServ Storage site and click the Support link for your product: http://www.hp.com/go/3par Common Provisioning Groups A Common Provisioning Group (CPG) is a shared pool of storage space (specifically, a virtual pool of logical disks) that allocates space to virtual volumes on demand. A CPG allows up to 4,095 virtual volumes to share the CPG's resources. You can create fully provisioned virtual volumes and Thinly Provisioned Virtual Volumes (TPVVs or Thin volumes) that draw space from a CPG's storage pool. Virtual Volumes Virtual volumes draw their resources from Common Provisioning Groups (CPGs). In order to make storage available to hosts, volumes are exported as Logical Unit Numbers (LUNs) to hosts. Virtual volumes are the only data layer visible to the hosts. You can create physical copies or virtual copy snapshots of virtual volumes; both types of copies remain available if the original base volume becomes unavailable. When you create virtual volumes, you must assign CPGs in order to allocate space to the virtual volumes. Therefore, to create virtual volumes, you must either use the default CPG created during the process of initializing the HP 3PAR StoreServ Storage system or create custom CPGs. 38 Storage Software Components