Dynamically provisioned volumes

Storage Subsystem Administration Guide for Hitachi NAS Platform

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A dynamically provisioned volume (DP-Vol) is a virtualized logical unit (LU) that is used with Hitachi Dynamic Provisioning (HDP). You create DP-Vols in a dynamically provisioned pool (a DP pool), which is an expandable collection of physical storage. The maximum capacity of an SD is 64TiB.

The total capacity of a DP-Vol can exceed that of the underlying parity groups or pool volumes (called thin provisioning).  Every DP-Vol can draw space from any of the underlying parity groups or pool volumes, so the system performs well even if the load on the SDs is unbalanced.

Hitachi Dynamic Provisioning (HDP) thin provisioning enables granular span-expansion without loss of performance, which is impossible without dynamic provisioning. The NAS server is aware of thin provisioning, and does not use more space than actually exists, making thin provisioning safe with a NAS server. With this server, unlike other server platforms, it is not necessary to expand a thickly provisioned HDP pool as soon as it becomes 70 percent full.