Acer PCI to Ultra SCSI RAID Controllers DAC960PG - Manual (Page 63)

Glossary
Manual No. 775012 G-5
Disk Array
A collection of disks from one or more commonly accessible disk systems.
Disk arrays, also known as RAID, allow disk drives to be used together to
improve fault tolerance, performance, or both. Disk arrays are commonly
used on servers and are becoming more popular on desktops and
workstations. See also Array.
Disk Drive
A device for the electronic digital storage of information.
Disk System
A storage system capable of supporting only disks.
Drive Groups, Drive Packs
A group of individual disk drives (preferably identical) that are logically tied
to each other and are addressed as a single unit. In some cases this may be
called a drive “pack” when referring to just the physical devices.
All the physical devices in a drive group should have the same size;
otherwise, each of the disks in the group will effectively have the capacity of
the smallest member. The total size of the drive group will be the size of the
smallest disk in the group multiplied by the number of disks in the group.
For example, if you have 4 disks of 400MB each and 1 disk of 200MB in a
pack, the effective capacity available for use is only 1000MB (5x200), not
1800MB.
Drivers
A software routine that receives I/O requests from higher levels within the
operating system and converts those requests to the protocol required by a
specific hardware device.
Dual Active
A pair of components, such as storage controllers in a failure tolerant storage
system, that share a task or set of tasks when both are functioning normally.
When one component of the pair fails, the other takes the entire load. Dual
active controllers (also called Active/Active controllers) are connected to the
same set of devices and provide a combination of higher I/O performance
and greater failure tolerance than a single controller.