HP 3PAR StoreServ 7400 4-node HP 3PAR StoreServ Storage Concepts Guide (OS 3.1 - Page 42
Virtual Volumes, Overview, Virtual Volume Types
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9 Virtual Volumes Overview Volumes draw their resources from Common Provisioning Groups (CPGs), and volumes are exported as Logical Unit Numbers (LUNs) to hosts. Virtual volumes are the only data layer visible to hosts. You can create physical copies or virtual copy snapshots of virtual volumes for use if the original base volume becomes unavailable. Before creating virtual volumes, you must first create CPGs to allocate space to the virtual volumes. For information about CPGs, see "Common Provisioning Groups" (page 39). You can organize volumes into autonomic groups that can be managed as one volume. If you have a group of volumes that require the same administrative procedures, it is easier to group those volumes into an autonomic group and manage them together. Creating virtual volumes can be performed with both the HP 3PAR Command Line Interface (CLI) and the HP 3PAR Management Console. Refer to the HP 3PAR Command Line Interface Administrator's Manual and the HP 3PAR Management Console Online Help for instructions on how to perform these tasks. For the maximum number of virtual volumes and virtual volume copies that can be created with your specific system configuration, go to the Single Point of Connectivity Knowledge (SPOCK) website http://www.hp.com/storage/spock. NOTE: Creating Thinly Provisioned Virtual Volumes (TPVVs) requires the HP 3PAR Thin Provisioning Software license. Creating virtual copies requires the HP 3PAR Virtual Copy Software license. For more information, see "HP 3PAR Software" (page 9). Virtual Volume Types There are three types of virtual volumes: • Fully provisioned virtual volumes • Thinly Provisioned Virtual Volumes (TPVVs) • Administrative Volumes Administrative volumes are created by the system and are for system usage only. Fully provisioned virtual volumes and TPVVs have three separate data components: • User space is the area of the volume that corresponds to the logical disk regions in the CPG available to the host. The user space contains the user data and is exported as a LUN to the host. • Snapshot space, also known as copy space, is the area of the volume that corresponds to logical disk regions in the CPG containing copies of user data that changed since the previous snapshot of the volume was created. The snapshot space contains the copy data. • Administration space, also known as admin space, is the area of the volume that corresponds to logical disk regions in the CPG that track changes to the volume since the previous snapshot was created. The administration space contains pointers to copies of user data in the snapshot space. Administration space is managed by the system, not with the tools you use to manage user and snapshot space. You can increase the size of volumes, the amount of user space, and the amount of snapshot space for volumes as the requirements increase. If the user space and snapshot space use all available space, the Virtual Copy feature's copy-on-write operation will fail. To avoid running out of user space, use TPVVs to automatically draw more user space from a CPG. The HP 3PAR OS automatically reclaims unused snapshot space from TPVVs and fully provisioned virtual volumes and returns the space to the logical disks. 42 Virtual Volumes