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Glossary 139
DUD
Acronym for driver update diskette. A DUD is an image of a diskette stored as a
regular file. To use it, you have to create the content to a real diskette from this
file. The steps used to create the diskette depend on how the image is supplied.
E
ECC Errors
Acronym for error correcting code. ECC errors occur in the memory and can
corrupt cached data so that it must be discarded. Single-bit ECC errors can be
handled by the firmware and do not disrupt normal operation. A notification is
sent if the number of single-bit errors exceeds a threshold value. ECC double-bit
errors are more serious, as they result in corrupted data and data loss.
Enclosure
A structure, such as a system, which contains physical disks that are grouped
together to create virtual disks.
Enclosure Management
Intelligent monitoring of the disk subsystem by software and/or hardware.
The disk subsystem can be part of the host system or can reside in an external
disk enclosure. Enclosure management helps you stay informed of events in
the disk subsystem, such as a physical disk or power supply failure.
Enclosure management increases the fault tolerance of the disk subsystem.
Exclusive-OR
A Boolean operation used to create a parity bit that can be used to restore data
affected by a damaged file or failed physical disk. The management utility
compares data from two physical disks and creates a parity bit that is stored on a
third physical disk. This operation is used for RAID levels that use parity bits,
such as RAID 5, which used distributed parity. Also known as X-OR.
F
Failed Physical Disk
A physical disk that has ceased to function, that consistently functions
improperly, or that is inaccessible.
Dell_PERC6.1_UG.book Page 139 Wednesday, April 15, 2009 4:18 PM