Dell PowerVault ME4 Series Storage System Administrator’s Guide

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Glossary of terms

The following table lists definitions of the terms used in ME4 Series publications:

Table 1. Glossary of ME4 Series termsME4 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.
AES	Advanced Encryption Standard.
AFA	All-flash array. A storage system that uses only SSDs, without tiering.
all-flash array	See also AFA.
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.
ALUA	Asymmetric Logical Unit Access.
array	See storage system.
ASC/ASCQ	Additional Sense Code/Additional Sense Code Qualifier. Information on sense data returned by a SCSI device.
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.
auto-write-through	See AWT
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. See also compatible disk, dedicated spare, dynamic spare, global 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	See 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.
CIM	Common Information Model .The data model for WBEM. It provides a common definition of management information for systems, networks, applications and services, and allows for vendor extensions.
CIMOM	Common Information Model Object Manager. A component in CIM that handles the interactions between management applications and providers.
CNC	Converged Network Controller. A controller module whose host ports can be set to operate in FC or iSCSI mode, using qualified SFP and cable options. Changing the host-port mode is also known as changing the ports’ personality.
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. See also available disk, dedicated spare, dynamic spare, global spare.
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 supercapacitor pack and flash memory; host, expansion, network, and service ports; and midplane connectivity.
CPLD	Complex programmable logic device.
CQL	CIM Query Language.
CRC	Cyclic Redundancy Check.
CRU	Customer-replaceable unit. 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. See also FRU.
CSV	Comma-separated values. A format to store tabular data in plain-text form.
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.
default mapping	Host-access settings that apply to all initiators that are not explicitly mapped to that volume using different settings. See also explicit mapping, masking.
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. See also linear disk group, virtual disk group, read cache.
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	See DSD.
DSD	Drive spin down. A power-saving feature available for non-ADAPT linear disk groups that monitors disk activity in the storage system and spins down inactive spinning disks based on user-selectable policies. Drive spin down is not applicable to disks in virtual pools.
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. See also available disk, compatible disk, dedicated spare, global spare.
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.
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. See also controller enclosure, expansion enclosure.
enclosure management processor	See EMP.
ESD	Electrostatic discharge.
ESM	Environmental Service Module. See IOM.
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.
explicit mapping	Access settings for a initiator that is explicitly mapped to a volume. See also default mapping, masking.
failback	See 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.
FC-AL	Fibre Channel.
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.
FRU	field-replaceable unit. 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. Product interfaces use the term “FRU” to refer to both FRUs and CRUs. See CRU.
Full Disk Encryption	See FDE.
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. See also available disk, compatible disk, dedicated spare, dynamic spare.
HBA	Host bus adapter. A device that facilitates I/O processing and physical connectivity between a host and the storage system.
host	A user-defined group of initiators that represents a server.
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.
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.
I/O Manager	An SNMP MIB term for a controller module.
I/O module	See IOM
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.
iSNS	Internet Storage Name Service.
JBOD	“Just a bunch of disks.” See expansion enclosure.
LBA	Logical block address. The address used for specifying the location of a block of data.
leftover	The state of a disk that the system has excluded from a disk group because the timestamp in the disk’s metadata 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 disk’s metadata 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 do not use paged-storage technology to virtualize data storage. The linear method stores 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.
linear disk group	For linear storage, a group of disks that is configured to use a specific RAID level. The number of disks that a linear disk group can contain is determined by its RAID level. Any supported RAID level can be used. When a linear disk group is created, a linear pool with the same name is also created to represent the volume-containment properties of the disk group. See also linear pool.
linear pool	For linear storage, a container for volumes that is composed of one linear disk group.
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	See FC-AL.
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	See MC.
map/mapping	Settings that specify whether a volume is presented as a storage device to a host system, and how the host system can access the volume. Mapping settings include an access type (read-write, read-only, or no access), controller host ports through which initiators may access the volume, and a LUN that identifies the volume to the host system. See also default mapping, explicit mapping, masking.
masking	A volume-mapping setting that specifies no access to that volume by hosts. See also default mapping, explicit mapping.
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. See also EC, SC.
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.
NTP	Network time protocol.
NV device	Nonvolatile device. The CompactFlash memory card in a controller module.
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	See PFU.
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. See also 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	See linear pool, virtual pool.
POST	Power-on self test. Tests that run immediately after a device is powered on.
primary system	The storage system that contains a replication set’s primary volume. See also replication set, secondary system.
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
quick rebuild	A virtual-storage feature that reduces the time that user data is less than fully fault-tolerant after a disk failure in a disk group. The quick-rebuild process rebuilds only data stripes that contain user data. Data stripes that have not been allocated to user data are rebuilt in the background.
RAID head	See controller enclosure.
RBOD	“RAID bunch of disks.” See controller enclosure.
read cache	A special disk group, comprised of SSDs, that can be added to a virtual pool for the purpose of speeding up read access to data stored on spinning disks elsewhere in the pool. Read cache is also referred to as read flash cache.
read flash cache	See read cache.
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 read cache.
remote syslog support	See syslog.
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	For virtual replication, 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 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.
RFC	Read flash cache. See read cache.
SAS	Serial Attached SCSI.
SBB	Storage Bridge Bay. A specification that standardizes physical, electrical, and enclosure-management aspects of storage enclosure design.
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 a replication set’s secondary volume. 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 use of the storage system’s 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.
SES	SCSI Enclosure Services. The protocol that allows the initiator to communicate with the enclosure using SCSI commands.
SFCB	Small Footprint CIM Broker.
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	See 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.
SMC	Storage Management Console. The web application that is embedded in each controller module and is the primary management interface for the storage system.
SMI-S	Storage Management Initiative - Specification. The SNIA standard that enables interoperable management of storage networks and storage devices. The interpretation of CIM for storage. It provides a consistent definition and structure of data, using object-oriented techniques. SMI-S is not supported for a system with 5U84 enclosures.
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 both the source volume and in its associated snap pool. A snapshot can be mapped and written to. Snapshots that can be mapped to hosts are counted against the snapshot 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.
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.
virtual pool	A container for volumes that is composed of one or more virtual disk groups.
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 mapping 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.
WBEM	Web-Based Enterprise Management.
WBI	Web-browser interface, called PowerVault Manager. The primary interface for managing the storage system. A user can enable the use of HTTP, HTTPS for increased security, or both.
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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Dell PowerVault ME4 Series Storage System Administrator’s Guide

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