Administrator Guide

Table 43. Glossary of ME4 Series terms (continued)
Term Definition
SNIA Storage Networking Industry Association. An association regarding storage networking
technology and applications.
source volume A volume that has snapshots. Used as a synonym for parent volume. SSD Solid-state drive.
SSH Secure Shell. A network protocol for secure data communication.
SSL Secure Sockets Layer. A cryptographic protocol that provides security over the internet.
standard volume A volume that can be mapped to initiators and presented as a storage device to a host system,
but is not enabled for snapshots.
Storage Controller See SC.
storage system A controller enclosure with at least one connected expansion enclosure. Product
documentation and interfaces use the terms storage system and system interchangeably.
syslog A protocol for sending event messages across an IP network to a logging server. This feature
supports User Datagram Protocol (UDP) but not Transmission Control Protocol (TCP).
thin provisioning A virtual-storage feature that allows actual storage for a virtual volume to be assigned as data
is written, rather than storage being assigned immediately for the eventual size of the volume.
This allows the storage administrator to overcommit physical storage, which in turn allows
the connected host system to operate as though it has more physical storage available than
is actually allocated to it. When physical resources fill up, the storage administrator can add
storage capacity on demand.
tier A homogeneous group of disks, typically of the same capacity and performance level, that
comprise one or more virtual disk groups in the same pool. Tiers differ in their performance,
capacity, and cost characteristics, which forms the basis for the choices that are made with
respect to which data is placed in which tier. The predefined tiers are:
● Performance, which uses SSDs (high speed)
● Standard, which uses enterprise-class spinning SAS disks (10k/15k RPM, higher capacity)
● Archive, which uses midline spinning SAS disks (<10k RPM, high capacity).
tier migration The automatic movement of blocks of data, associated with a single virtual volume, between
tiers based on the access patterns that are detected for the data on that volume.
tray See enclosure.
ULP Unified LUN Presentation. A RAID controller feature that enables a host system to access
mapped volumes through any controller host port. ULP incorporates ALUA extensions.
undercommitted The amount of storage capacity that is allocated to volumes is less than the physical capacity
of the storage system.
unmount To remove access to a volume from a host OS.
unwritable cache data Cache data that has not been written to disk and is associated with a volume that no longer
exists or whose disks are not online. If the data is needed, the volume’s disks must be brought
online. If the data is not needed it can be cleared, in which case it will be lost and data will
differ between the host system and disk. Unwritable cache data is also called orphan data.
UPS Uninterruptible power supply.
UTC Coordinated Universal Time.
UTF-8 UCS transformation format - 8-bit. A variable-width encoding that can represent every
character in the Unicode character set used for the PowerVault Manager and CLI.
vdisk See linear disk group.
virtual The storage-class designation for logical components such as volumes that use paged-storage
technology to virtualize data storage. See paged storage.
virtual disk group A group of disks that is configured to use a specific RAID level. The number of disks that a
virtual disk group can contain is determined by its RAID level. A virtual disk group can be added
to a new or existing virtual pool. See also virtual pool.
Glossary of terms 189