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Glossary 22
degraded A redundant array (for example, a RAID 1 array) in which one or more members have failed.
The data is intact, but redundancy has been compromised. Any further failure would cause the
array to fail and result in data loss.
dirty data Data that has been written to a cache, but which has not been flushed out to its final
destination.
disk A nonremovable platter in a hard drive, or removable media used in a CD drive, floppy disk
drive, or Zip drive. See also disk ID, drive, and hard disk, hard drive.
disk ID Unique disk identifier that consists of the channel number, ID, and LUN (channel:ID:LUN), for
example, 1:04:0. See also channel.
drive Device used for storing data. May contain one or more removable or nonremovable, writable,
or read-only media. See also hard disk, hard drive.
drive LED Indicator light that illuminates during read or write operations.
event Notification or alert from the system, indicating that a change has occurred.
event log File used to maintain information about prior controller activities or errors.
event notification Process for transmitting events.
failed State of a nonredundant array that has suffered a single drive failure, or a redundant array
that has suffered multiple drive failures. A failed array is inaccessible and data is lost.
failed partition A partition that is no longer usable by an array because it is either logically bad and therefore
no longer needed, or physically damaged.
failover drive See hotspare.
fault-tolerant array Refers to an array that can continue to function after a disk drive failure without loss of data.
See also redundant.
foreign disk Disk that has previously been initialized on another SATA RAID controller. The RAID signature
on the disk allows the controller to identify whether or not the disk was initialized on the
controller to which it is currently connected.
free space/partition See available space/partition.
hard disk, hard
drive
Basic unit of nonvolatile, nonremovable, magnetic storage media. See also drive.
hot plug, hot swap To remove a component from a system and install a new component while the power is on
and the system is running.
hotspare A hard drive that is present as an array member, but which is not used in day-to-day data
storage. Instead, it is reserved for use as an automatic replacement drive if any of the other
drives in the array fail. There are two types of hotspares: Global hotspares protect every array
that they have enough capacity to protect, while dedicated hotspares protect only the array to
which they are assigned.