Mega
A notation denoting a multiplier of 1 million (1,000,000).
metadata
Information that a controller pair writes on the disk array. This information is
used to control and monitor the array and is not readable by the host.
micro meter
See
µm
.
mirrored caching
A process in which half of each controller’s write cache mirrors the companion
controller’s write cache. The total memory available for cached write data is
reduced by half, but the level of protection is greater.
mirroring
The act of creating an exact copy or image of data.
MTBF
Mean Time Between Failures. The average time from start of use to first failure
in a large population of identical systems, components, or devices.
multi-mode fiber
A fiber optic cable with a diameter large enough (50 microns or more) to allow
multiple streams of light to travel different paths from the transmitter to the receiver.
This transmission mode enables bidirectional transmissions.
Network Storage
Controller
See
NSC
.
NONCRITICAL
Condition
A drive enclosure EMU condition report that occurs when one or more elements
inside the enclosure have failed or are operating outside of their specifications.
The failure does not affect continued normal operation of the enclosure. All
devices in the enclosure continue to operate according to their specifications.
The ability of the devices to operate correctly may be reduced if additional
failures occur. UNRECOVERABLE and CRITICAL errors have precedence over
this condition. This condition has precedence over INFORMATION condition.
Early correction can prevent the loss of data.
node port
A device port that can operate on the arbitrated loop topology.
non-OFC (Open
Fibre Control)
A laser transceiver whose lower-intensity output does not require special open
Fibre Channel mechanisms for eye protection. The Enterprise storage system
transceivers are non-OFC compatible.
NSC
Network Storage Controller. The HSV Controllers used by the Enterprise storage
system.
NVRAM
Nonvolatile Random Access Memory. Memory whose contents are not lost when
a system is turned Off or if there is a power failure. This is achieved through the
use of UPS batteries or implementation technology such as flash memory. NVRAM
is commonly used to store important configuration parameters.
occupancy alarm
level
A percentage of the total disk group capacity in blocks. When the number of
blocks in the disk group that contain user data reaches this level, an event code
is generated. The alarm level is specified by the user.
OCP
Operator Control Panel. The element that displays the controller’s status using
indicators and an LCD. Information selection and data entry is controlled by the
OCP push-button.
online/nearonline
An online drive is a normal, high-performance drive, while a near-online drive
is a lower-performance drive.
Glossary
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