HP 3PAR Operating System Software - Manual (Page 40)

11 Virtual Volumes
Virtual volumes are the only data layer visible to host systems.
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Virtual volumes draw storage space from Common Provisioning Groups (CPGs).
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Virtual volumes become visible to host systems when you export (present) them to hosts.
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Virtual volumes are exported as Logical Unit Numbers (LUNs) to hosts.
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You can create physical copies or virtual copies (snapshots) of virtual volumes. These copies
are backup in case the original base volume becomes unavailable.
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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:
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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);
the size limit is 16 TiB.
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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 TiB.
Monitoring Thin Volume Growth
Thin volumes require careful planning and monitoring to prevent them from becoming so large
that either they set off the HP 3PAR StoreServ Storage system's built-in safety mechanisms or
writes to the volumes fail. To restrict a Thin volume’s growth:
◦ Set an allocation warning
◦ Set an allocation limit , and ensure 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.
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Administrative volumes are created by the system and are for system usage only.
40 Virtual Volumes