MSA 2040 SMU Reference Guide

Glossary 181
DSD Drive spin down. A power-saving feature that monitors disk activity in the storage system
and spins down inactive disks based on user-selectable policies.
dual-port disk A disk that is connected to both controllers so it has two data paths, achieving fault
tolerance.
Dynamic Host
Configuration Protocol
See DHCP.
dynamic spare An available compatible disk that is automatically assigned, if the dynamic spares option is
enabled, to replace a failed disk in a vdisk with a fault-tolerant RAID level. See also
available disk, compatible disk, dedicated spare, and global spare.
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, MC, and SC.
EMP Enclosure management processor. An EC 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
See EMP.
Expander Controller See EC.
expansion enclosure See drive enclosure.
expansion module A FRU that contains the following subsystems and devices: a SAS expander and EC
processor; host, expansion, and service ports; and midplane connectivity. In a drive
enclosure, the upper expansion module is designated A and the lower one is designated B.
explicit mapping Access settings for a host to a volume that override the volume’s default mapping. See also
default mapping and masking.
extrinsic methods Methods which are particular to a specific class in SMI-S. See also intrinsic methods.
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 volumes, cache data, host ID information, and LUNs and
WWNs. See recovery.
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 method by which you can secure the data residing on a system. See
also lock key, passphrase, and repurpose.
Fibre Channel
Arbitrated Loop
See FC-AL.
field-programmable
gate array
See FPGA.
field-replaceable unit See FRU.
FPGA Field-programmable gate array. An integrated circuit designed to be configured after
manufacturing.
FRU Field-replaceable unit. A part that can be removed and replaced by the user or support
technician without having to send the product to a repair facility.
Full Disk Encryption See FDE.
global spare A compatible disk that is reserved for use by any vdisk with a fault-tolerant RAID level to
replace a failed disk. See also available disk, compatible disk, dedicated spare, and
dynamic spare.
HBA Host bus adapter. A device that facilitates I/O processing and physical connectivity
between a host and the storage system.