HP 3PAR StoreServ 7400 2-node HP 3PAR StoreServ 7000 SmartStart 1.2 User&# - Page 47
Virtual Volumes, Virtual Volume Types, Monitoring Thin Volume Growth
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11 Virtual Volumes Virtual volumes are the only data layer visible to host systems. • Virtual volumes draw storage space from CPGs. • Virtual volumes become visible to host systems when you export (present) them to hosts. • Virtual volumes are exported as LUNs to hosts. • You can create physical copies or virtual copies (snapshots) of virtual volumes. These copies serve as backups in case the original base volume becomes unavailable. • If you have multiple volumes that require the same administrative procedures, you can group those volumes into an autonomic group and manage them together, as one volume. To create and manage virtual volumes, use the HP 3PAR Management Console. For more information, see the HP 3PAR Management Console Online Help. Virtual Volume Types There are three types of virtual volumes used directly for data storage: • Fully provisioned virtual volumes have a set amount of allocated user space. Fully provisioned virtual volumes require the HP 3PAR StoreServ Storage system to reserve the entire amount of storage space configured for the volumes, whether or not the space is actually used. The size of each fully provisioned virtual volume size is fixed (and not dynamic, like a Thin volume), and the size limit is 16 TB. • Thinly Provisioned Virtual Volumes (TPVVs or Thin volumes) draw space from the associated CPG pools as needed. CPGs allocate space on demand to Thin volumes in small increments for each controller node, but can adjust the size of these increments based on the rate of consumption (allocating more space during periods of high consumption and less space during periods of low consumption). As the volumes that draw space from the CPG require additional storage, the HP 3PAR OS automatically adds more storage space to the CPG until the CPG reaches its growth limit. The Thin volume size limit is 16 TB. Monitoring Thin Volume Growth Thin volumes require careful planning and monitoring to prevent them from becoming so large that they set off the HP 3PAR StoreServ Storage system's built-in safety mechanisms or that writes to the volumes fail. To restrict a Thin volume's growth: ◦ Set an allocation warning. ◦ Set an allocation limit and ensure that this limit does not exceed the associated CPG's growth limit. ◦ Continue to monitor Thin volume growth. Creating Thin volumes requires the HP 3PAR Thin Provisioning Software license. • Administrative volumes are created by the system and are for system usage only. Virtual Volume Types 47