Dell PowerVault ME5 Series Administrator's Guide

Glossary of terms

The following table lists definitions of the terms used in ME5 Series publications:

Table 1. Glossary of ME5 Series termsME5 Series glossary of terms
Term	Definition
2U12	An enclosure that is two rack units in height and can contain 12 disks.
2U24	An enclosure that is two rack units in height and can contain 24 disks.
5U84	An enclosure that is five rack units in height and can contain 84 disks.
ADAPT	A RAID-based data protection level that maximizes flexibility, provides built in spare capacity, and allows for very fast rebuilds, large storage pools, and simplified expansion.
AES	Advanced Encryption Standard.
AFA	All-flash array. A storage system that uses only SSDs, without tiering.
all-flash array	All-flash array (AFA). A storage system that uses only SSDs, without tiering.
allocated page	A page of virtual pool space that has been allocated to a volume to store data.
allocation rate	The rate, in pages per minute, at which a virtual pool is allocating pages to its volumes because they need more space to store data.
array	See storage system.
ASC/ASCQ	Additional Sense Code/Additional Sense Code Qualifier. Information on sense data returned by a SCSI device.
atomic write	A write-optimization mode for volume cache that guarantees if a failure (such as I/O being aborted or a controller failure)interrupts a data transfer between a host system and the storage system, controller cache will contain either all the old data or all the new data, not a mix of old and new data. This option has a slight performance cost because it maintains a secondary copy of data in cache so that if a data transfer is not completed, the old cache data can be restored.
auto-write-through	Auto-write-through (AWT). A setting that specifies when the RAID controller cache mode automatically changes from write-back to write-through.
automated tiered storage	A virtual-storage feature that automatically uses the appropriate tier of disks to store data based on how frequently the data is accessed. This enables higher-cost, higher-speed disks to be used only for frequently needed data, while infrequently needed data can reside in lower-cost, lower-speed disks.
available disk	A disk that is not a member of a disk group, is not configured as a spare, and is not in the leftover state. It is available to be configured as a part of a disk group or as a spare.
AWT	Auto-write-through. A setting that specifies when the RAID controller cache mode automatically changes from write-back to write-through.
base volume	A virtual volume that is not a snapshot of any other volume, and is the root of a snapshot tree.
canister	Synonym for IOM.
CAPI	Configuration Application Programming Interface. A proprietary protocol used for communication between the Storage Controller and the Management Controller in a controller module. CAPI is always enabled.
CHAP	Challenge-Handshake Authentication Protocol.
chassis	The sheet metal housing of an enclosure.
child volume	The snapshot of a parent volume in a snapshot tree. See parent volume.
chunk size	The amount of contiguous data that is written to a disk group member before moving to the next member of the disk group.
compatible disk	A disk that can be used to replace a failed member disk of a disk group because it has at least the same capacity as, and is of the same type (enterprise SAS, for example) as, the disk that failed.
controller A (or B)	A short way of referring to controller module A (or B).
controller enclosure	An enclosure that contains one or two controller modules.
controller module	A FRU that contains the following subsystems and devices: a Storage Controller processor; a Management Controller processor; a SAS expander and Expander Controller processor; management interfaces; cache protected by a super capacitorpack and non-volatile memory; host, expansion, network, and service ports; and midplane connectivity.
CPLD	Complex programmable logic device.
CRC	Cyclic Redundancy Check.
CRU	Customer-replaceable unit. See customer FRU.
CSV	Comma-separated values. A format to store tabular data in plain-text form.
customer FRU	A product module that can be ordered as a SKU and replaced in an enclosure by customers or by qualified service personnel, without having to send the enclosure to a repair facility.
DAS	Direct Attached Storage. A dedicated storage device that connects directly to a host without the use of a switch.
deallocation rate	The rate, in pages per minute, at which a virtual pool is deallocating pages from its volumes because they no longer need the space to store data.
dedicated spare	A disk that is reserved for use by a specific linear disk group to replace a failed disk. See also available disk, compatible disk, dynamic spare, global spare.
DES	Data Encryption Standard.
DHCP	Dynamic Host Configuration Protocol. A network configuration protocol for hosts on IP networks.
disk group	A group of disks that is configured to use a specific RAID level and provides storage capacity for a pool. The number of disks that a disk group can contain is determined by its RAID level.
disk spin down	Disk spin down (DSD). A power-saving feature for spinning disks that monitors disk activity and spins down inactive disks based on user-selectable policies.
DNS	Domain Name System.
drain	The automatic movement of active volume data from a virtual disk group to other disk-group members within the same pool.
drawer	In a 5U84 enclosure, one of two FRUs that each holds 42 disks
drive enclosure	See expansion enclosure. See also EBOD, JBOD.
drive spin down	Disk spin down (DSD). A power-saving feature for spinning disks that monitors disk activity and spins down inactive disks based on user-selectable policies
DRM	Disaster recovery management. Storage-system firmware features that, when the Site Replication Adapter (SRA) feature is enabled, support the use of VMware Site Recovery Manager to automate disaster-recovery failover and failback tasks. See also SRA.
DSD	Disk spin down (DSD). A power-saving feature for spinning disks that monitors disk activity and spins down inactive disks based on user-selectable policies.
DSP	Digital signal processor.
dual-port disk	A disk that is connected to both controllers so it has two data paths, achieving fault tolerance.
dynamic spare	An available compatible disk that is automatically assigned, if the dynamic spares option is enabled, to replace a failed disk in a disk group with a fault-tolerant RAID level.
EBOD	Expanded Bunch of Disks. Expansion enclosure attached to a controller enclosure.
EC	Expander Controller. A processor (located in the SAS expander in each controller module and expansion module) that controls the SAS expander and provides SES functionality. See also EMP.
EEPROM	Electrically erasable programmable ROM.
eMMC	Embedded MultiMedia card. Also referred to as memory card, non-volatile memory.
EMP	Enclosure management processor. An Expander Controller subsystem that provides SES data such as temperature, power supply and fan status, and the presence or absence of disks.
enclosure	A physical storage device that contains I/O modules, disk drives, and other FRUs.
enclosure management processor	Enclosure management processor (EMP). An Expander Controller subsystem that provides SES data such as temperature, power supply and fan status, and the presence or absence of disks
ESD	Electrostatic discharge.
Expander Controller	See EC.
expansion enclosure	An enclosure that contains one or two expansion modules. Expansion enclosures can be connected to a controller enclosure to provide additional storage capacity. See also EBOD, JBOD.
expansion module	A FRU that contains the following subsystems and devices: a SAS expander and Expander Controller processor; host, expansion, and service ports; and midplane connectivity. In an expansion enclosure, the upper expansion module is designated A and the lower one is designated B.
failback	Synonym for recovery.
failover	In an active-active configuration, failover is the act of temporarily transferring ownership of controller resources from an offline controller to its partner controller, which remains operational. The resources include pools, volumes, cache data, host ID information, and LUNs and WWNs. See also recovery.
fan module	The fan FRU used in 5U84 enclosures. There are five in each enclosure, separate from the PSUs.
FC	Fibre Channel interface protocol.
FC-AL	Fibre Channel Arbitrated Loop. The FC topology in which devices are connected in a one-way loop.
FDE	Full Disk Encryption. A feature that secures all the user data on a storage system. See also lock key, passphrase, repurpose, SED.
FPGA	Field-programmable gate array. An integrated circuit designed to be configured after manufacturing.
FQDN	Fully qualified domain name.
FRU	Field-replaceable unit. See service FRU.
Full Disk Encryption	Full Disk Encryption (FDE). A feature that secures all the user data on a storage system. See also lock key, passphrase, repurpose, SED.
GEM	Generic Enclosure Management. The firmware responsible for managing enclosure electronics and environmental parameters. GEM is used by the Expander Controller.
global spare	A compatible disk that is reserved for use by any disk group with a fault-tolerant RAID level to replace a failed disk.
HBA	Host bus adapter. A device that facilitates I/O processing and physical connectivity between a host and the storage system.
HDD	Hard disk drive
host	A user-defined object that represents a server to which the storage system is attached, and is used to define a mapping relationship to storage.
host group	A user-defined group of hosts for ease of management, such as for mapping operations.
host port	A port on a controller module that interfaces to a host computer, either directly or through a network switch.
I/O Manager	An SNMP MIB term for a controller module.
I/O module	Input/output module (I/O module, IOM). An IOM can be either a controller module or an expansion module
initiator	An external port to which the storage system is connected. The external port may be a port in an I/O adapter in a server, or a port in a network switch.
IOM	Input/output module, or I/O module. An IOM can be either a controller module or an expansion module.
IOPS	I/O operations per second.
IQN	iSCSI Qualified Name.
iSCSI	Internet SCSi interface protocol
ISE	Instant Secure Erase. A feature designed to protect data on hard disk drives by instantly resetting the drive back to factory settings and changing the encryption key so that any data remaining on the drive is cryptographically erased. This means all data on the drive is permanently and instantly unreadable, as needed
iSNS	Internet Storage Name Service.
JBOD	“Just a bunch of disks.” An expansion enclosure attached to a server.
LBA	Logical block address. The address used for specifying the location of a block of data.
LDAP	Local directory access protocol.
LDAPS	LDAP over SSL.
leftover	The state of a disk that the system has excluded from a disk group because the timestamp in the metadata on the disk is older than the timestamp of other disks in the disk group, or because the disk was not detected during a rescan. A leftover disk cannot be used in another disk group until the metadata on the disk is cleared. For information and cautions about doing so, see documentation topics about clearing disk metadata.
LFF	Large form factor.
linear	The storage-class designation for logical components such as volumes that store user data in sequential, fully allocated physical blocks, using a fixed (static) mapping between the logical data presented to hosts and the physical storage where it is stored.
LIP	Loop Initialization Primitive. An FC primitive used to determine the loop ID for a controller.
lock key	A system-generated value that manages the encryption and decryption of data on FDE-capable disks. See also FDE, passphrase.
loop	Fibre Channel Arbitrated Loop. The FC topology in which devices are connected in a one-way loop.
LUN	Logical Unit Number. A number that identifies a mapped volume to a host system.
MAC address	Media Access Control Address. A unique identifier assigned to network interfaces for communication on a network.
Management Controller	Management Controller (MC). A processor (located in a controller module) that is responsible for human-computer interfaces, such as a WBI, and computer-computer interfaces, such as SNMP, and interacts with the Storage Controller.
map	Settings that specify whether a volume is presented as a storage device to a host, and how the host can access the volume. Mapping settings include an access type and a LUN that identifies the volume to the host.
MC	Management Controller. A processor (located in a controller module) that is responsible for human-computer interfaces, such as the PowerVault Manager, and computer-computer interfaces, such as SNMP, and interacts with the Storage Controller.
metadata	Data in the first sectors of a disk that stores disk-, disk-group-, and volume-specific information including disk group membership or spare identification, disk group ownership, volumes and snapshots in the disk group, host mapping of volumes, and results of the last media scrub.
MIB	Management Information Base. A database used for managing the entities in SNMP. midplane The printed circuit board to which components connect in the middle of an enclosure. mount To enable access to a volume from a host OS. See also host, map/mapping, volume.
midplane	The printed circuit board to which components connect in the middle of an enclosure.
mount	To enable access to a volume from a host OS. See also host, map/mapping, volume.
network port	The Ethernet port on a controller module through which its Management Controller is connected to the network.
NRAID	Non-RAID, non-striped mapping to a single disk.
NTP	Network time protocol.
OID	Object Identifier. In SNMP, an identifier for an object in a MIB.
orphan data	See unwritable cache data.
overcommit	A setting that controls whether a virtual pool is allowed to have volumes whose total size exceeds the physical capacity of the pool.
overcommitted	The amount of storage capacity that is allocated to virtual volumes exceeds the physical capacity of the storage system.
page	A range of contiguous LBAs in a virtual disk group.
paged storage	A method of mapping logical host requests to physical storage that maps the requests to virtualized “pages” of storage that are in turn mapped to physical storage. This provides more flexibility for expanding capacity and automatically moving data than the traditional, linear method in which requests are directly mapped to storage devices. Paged storage is also called virtual storage.
parent volume	A virtual volume that has snapshots (can be either a base volume or a base snapshot volume). The parent of a snapshot is its immediate ancestor in the snapshot tree.
partner firmware update	Partner firmware update (PFU). The automatic update of the partner controller when the user updates firmware on one controller.
passphrase	A user-created password that allows users to manage lock keys in an FDE-capable system. See also FDE, lock key.
PCB	Printed circuit board.
PCBA	Printed circuit board assembly.
PCM	Power and cooling module FRU. A power supply module that includes an integrated fan. See also PSU.
PDU	Power distribution unit. The rack power-distribution source to which a PCM or PSU connects.
peer connection	The configurable entity defining a peer-to-peer relationship between two systems for the purpose of establishing an asynchronous replication relationship. See also peer system.
peer system	A remote storage system that can be accessed by the local system and is a candidate for asynchronous replications. Both systems in a peer connection are considered peer systems to each other, and they both maintain a peer connection with the other. Asynchronous replication of volumes may occur in either direction between peer systems configured in a peer connection.
PFU	Partner firmware update. The automatic update of the partner controller when the user updates firmware on one controller.
PGR	Persistent group reservations.
PHY	One of two hardware components that form a physical link between devices in a SAS network that enables transmission of data.
point-to-point	Fibre Channel Point-to-Point topology in which two ports are directly connected.
pool	container for volumes that is composed of one or more virtual disk groups.
POST	Power-on self test. Tests that run immediately after a device is powered on.
PowerVault Manager	PowerVault Manager is the web-browser interface (WBI), the web application that is embedded in each controller module and is the primary management interface for the storage system
primary system	The storage system that contains the primary volume of a replication set.
primary volume	The volume that is the source of data in a replication set and that can be mapped to hosts. The primary volume exists in a primary (linear storage) or pool (virtual storage) in the primary storage system.
PSU	Power supply unit FRU.
RAID head	Synonym for controller enclosure.
RBOD	“RAID bunch of disks.” See controller enclosure.
read cache	A special virtual disk group, comprised of SSDs, that can be added to a pool for the purpose of speeding up read access to data stored on spinning disks elsewhere in the pool.
recovery	In an active-active configuration, recovery is the act of returning ownership of controller resources to a controller (which was offline) from its partner controller. The resources include volumes, cache data, host ID information, and LUNs and WWNs. See also failover.
replication	Asynchronous replication of block-level data from a volume in a primary system to a volume in a secondary system by creating an internal snapshot of the primary volume and copying the snapshot data to the secondary system via Fibre Channel or iSCSI links.
replication set	A container that houses the infrastructure upon which replications are performed. It defines a relationship between a primary and secondary volume for the purposes of maintaining a remote copy of the primary volume on a peer system. See primary volume, secondary volume.
replication set failover	The secondary system of a replication set has allowed direct access to the secondary volume or volume group because the primary system is not operational. In this state no replications will occur, even if the primary system becomes operational and communication is restored. The secondary volume can be mapped and accessed for use, including rollback to the contents of any manually created or snapshot-history snapshot.
replication snapshot history	As part of handling a replication, the replication set will automatically take a snapshot of the primary and/or secondary volume, thereby creating a history of data that has been replicated over time. This feature can be enabled for a secondary volume or for a primary volume and its secondary volume, but not for a volume group.
repurpose	A method by which all data on a system or disk is erased in an FDE-capable system. Repurposing unsecures the system and disks without needing the correct passphrase. See also FDE, passphrase.
SAS	Serial Attached SCSI.
SATA	Serial ATA.
SC	Storage Controller. A processor (located in a controller module) that is responsible for RAID controller functions. The SC is also referred to as the RAID controller. See also EC, MC.
secondary system	The storage system that contains the secondary volume of a replication set. See also replication set, primary system.
secondary volume	The volume that is the destination for data in a replication set and that is not accessible to hosts. The secondary volume exists in a secondary (linear storage) or pool (virtual storage) in a secondary storage system.
secret	For use with CHAP, a password that is shared between an initiator and a target to enable authentication.
SED	Self-encrypting drive. A disk drive that provides hardware-based data encryption and supports the Full Disk Encryption feature. See also FDE.
SEEPROM	Serial electrically erasable programmable ROM. A type of nonvolatile (persistent if power removed) computer memory used as FRU ID devices.
service FRU	A product module that can be replaced in an enclosure by qualified service personnel only, without having to send the enclosure to a repair facility.
service tag	An alphanumeric string that uniquely identifies the product and is used to appropriately route support cases.
SES	SCSI Enclosure Services. The protocol that allows the initiator to communicate with the enclosure using SCSI commands.
SFF	Small form factor.
SFTP	SSH File Transfer Protocol. A secure secondary interface for installing firmware updates, downloading logs, and installing security certificates and keys. All data sent between the client and server will be encrypted.
SHA	Secure Hash Algorithm.
shelf	Synonym for enclosure.
sideplane	A printed circuit board to which components connect longitudinally within an enclosure.
SLP	Service Location Protocol. Enables computers and other devices to find services in a local area network without prior configuration.
SMART	Self-Monitoring Analysis and Reporting Technology. A monitoring system for disk drives that monitors reliability indicators for the purpose of anticipating disk failures and reporting those potential failures.
snapshot	A point-in-time copy of the data in a source volume that preserves the state of the data as it existed when the snapshot was created. Data associated with a snapshot is recorded in the source volume. A snapshot can be mapped and written to. Snapshots that can be mapped to hosts are counted against the snapshot-license limit, whereas transient and unmappable snapshots are not.
snapshot tree	A group of virtual volumes that are interrelated due to creation of snapshots. Since snapshots can be taken of existing snapshots, volume inter-relationships can be thought of as a “tree” of volumes. A tree can be 254 levels deep. See also base volume, child volume, parent volume, source volume.
source volume	A volume that has snapshots. Used as a synonym for parent volume.
SRA	Storage Replication Adapter. A host-based software component that allows VMware Site Recovery Manager to manage the disaster recovery management (DRM) features of the storage-system firmware, automating disaster-recovery failover and failback tasks. The SRA uses the CLI XML API to control the storage system. See also DRM.
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	Storage Controller. A processor (located in a controller module) that is responsible for RAID controller functions. The SC is also referred to as the RAID controller. See also EC, MC.
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).
TCP	Transmission Control Protocol.
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; Standard, which uses enterprise-class spinning SAS disks; Archive, which uses midline spinning SAS disks.
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	Synonym for enclosure.
UDP	User Datagram Protocol.
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. Synonyms include unpresent and unmap.
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 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 interfaces.
virtual	The storage-class designation for logical components such as volumes that use paged-storage technology to virtualize data storage. See paged storage.
volume	A logical representation of a fixed-size, contiguous span of storage that is presented to host systems for the purpose of storing data.
volume copy	An independent copy of the data in a linear volume. The capability to copy volumes makes use of snapshot functionality.
volume group	A user-defined group of volumes for ease of management, such as for host-attachment operations.
VPD	Vital Product Data. Data held on an EEPROM in an enclosure or FRU that is used by GEM to identify and control the component.
WBI	PowerVault Manager is the web-browser interface (WBI), the web application that is embedded in each controller module and is the primary management interface for the storage system.
WWN	World Wide Name. A globally unique 64-bit number that identifies a device used in storage technology.
WWNN	World Wide Node Name. A globally unique 64-bit number that identifies a device.
WWPN	World Wide Port Name. A globally unique 64-bit number that identifies a port.

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