Appendix B. Terminology 835
Unique identifier
A unique identifier (UID) is an identifier that is assigned to storage-system logical units when
they are created. It is used to identify the logical unit regardless of the logical unit number
(LUN), the status of the logical unit, or whether alternate paths exist to the same device.
Typically, a UID is used only once.
Virtualization
In the storage industry, virtualization is a concept in which a pool of storage is created that
contains several storage systems. Storage systems from various vendors can be used. The
pool can be split into volumes that are visible to the host systems that use them. See also
“Capacity licensing” on page 820.
Virtualized storage
Virtualized storage is physical storage that has virtualization techniques applied to it by a
virtualization engine.
Virtual local area network
Virtual local area network (VLAN) tagging separates network traffic at the layer 2 level for
Ethernet transport. The system supports VLAN configuration on both IPv4 and IPv6
connections.
Virtual Storage Area Network
A virtual Storage Area Network (VSAN) is a logical fabric entity defined within the storage
area network (SAN). It can be defined on a single physical SAN switch or across multiple
physical switched or directors. In VMware terminology the vSAN is defined as a logical layer
of storage capacity built from physical disk drives attached directly into the ESXi hosts. This
solution is not considered for the scope of our publication.
Vital product data
Vital product data (VPD or VDP) is information that uniquely defines system, hardware,
software, and microcode elements of a processing system.
Volume
A volume is an IBM Storwize V5000 logical device that appears to host systems that are
attached to the SAN as a SCSI disk. Each volume is associated with exactly one I/O Group. A
volume has a preferred node within the I/O Group.
Volume copy
A volume copy is a physical copy of the data that is stored on a volume. Mirrored volumes
have two copies. Non-mirrored volumes have one copy.
Volume protection
To prevent active volumes or host mappings from inadvertent deletion, the system supports a
global setting that prevents these objects from being deleted if the system detects that they
have recent I/O activity. When you delete a volume, the system checks to verify whether it is
part of a host mapping, FlashCopy mapping, or remote-copy relationship. In these cases, the
system fails to delete the volume, unless the -force parameter is specified. Using the -force
parameter can lead to unintentional deletions of volumes that are still active. Active means
that the system detected recent I/O activity to the volume from any host.
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