Volumes - IBM V7000 Introduction And Implementation Manual

A multi-tiered storage pool is used to enable automatic migration of extents between disk tiers
using the IBM Flex System V7000 Storage Node Easy Tier function. Figure 2-14 shows these
components.
Figure 2-14 IBM Flex System V7000 Storage Node with single tier and multi tier pools

2.6.9 Volumes

A volume is a virtual logical disk that is presented to a host system by the clustered system. In
our virtualized environment, the host system has a volume mapped to it by IBM Flex System
V7000 Storage Node. IBM Flex System V7000 Storage Node translates this volume into a
number of extents, which are allocated across MDisks. The advantage with storage
virtualization is that the host is "decoupled" from the underlying storage, so the virtualization
appliance can move the extents around without impacting the host system.
The host system cannot directly access the underlying MDisks in the same manner as it could
access RAID arrays in a traditional storage environment.
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Chapter 2. Introduction to IBM Flex System V7000 Storage Node