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Glossary

Dell OpenManage™ Array Manager 2.5 User's Guide

Use this glossary to find the definitions of terms pertinent to Array Manager.

Active partition

The partition from which the computer starts up. The active partition must be a primary partition on a basic disk. If you use Windows NT or Windows 2000 exclusively, the active partition can be the same as the system partition. If you have a dual-boot system with two operating systems (such as Windows 2000 and Windows NT OR Windows NT and Windows 98 or MS-DOS) the active partition must contain the startup files for both operating systems.

Array

The term array refers to a RAID controller. It can also refer more generally to the physical disks and other hardware that are associated with the controller, as well as the logical disks (known as virtual disks) that are derived from the controller's physical disks.

Array disk

A physical disk controlled by a RAID controller. These disks can be placed in an array group, and virtual disks can be created from them.

Array group

An array group provides a mechanism to group disks that are controlled by a particular RAID controller. You can create virtual disks from disks in an array group.

Basic disk

A physical disk that can contain primary partitions, an extended partition, and logical drives. See also basic volume; extended partition; logical drive; primary partition.

Basic volume

A logical volume or partition created on a basic disk. You can create basic volumes only on basic disks. See also basic disk; volume.

Boot volume

The volume, formatted for either an NTFS or FAT file system, that contains the Windows NT/2000 operating system and its support files. The boot volume can be the same as the system volume. See also FAT; NTFS; system volume; volume.

Concatenation

Storing data either on one disk (simple) or on disk space that spans more than one disk (spanned).

Dell Utility Partition

This is a factory-installed, bootable partition on the hard-disk drive that provides utilities and diagnostics for your Dell PowerEdge™ system. When activated, the partition boots and provides an executable environment for the partition's utilities.

Disk

A physical data storage device attached to a computer. See also basic disk; dynamic disk.

Disk striping

Disk striping writes data across multiple disk drives instead of just one disk. Disk striping involves partitioning each drive storage space into stripes that can vary in size. These stripes are interleaved in a repeated, sequential manner. The combined storage space is composed of stripes from each drive.

Dynamic disk

A logical disk that is managed by Array Manager software. Dynamic disks can contain only dynamic volumes (that is, volumes created with Array Manager software). Dynamic disks cannot contain partitions or logical drives, nor can they be accessed by MS-DOS or Windows 95/98. See also dynamic volume; partition.

Dynamic group

A dynamic group contains dynamic disks and dynamic volumes.

Dynamic volume

A logical volume that is created with Array Manager software. Dynamic volumes include simple, spanned, striped, mirrored, and RAID-5. You must create dynamic volumes on dynamic disks. See also dynamic disk; volume.

Encapsulation

The process of upgrading partitions and NT 4.0 Disk Administrator RAID volumes to dynamic volumes by upgrading the disk(s) they are on to dynamic. See the section Upgrade Disks with Legacy Volumes to Dynamic in the Volume Management chapter for details.

Extended partition

A portion of a basic disk that can contain logical drives. Use an extended partition if you want to have more than four volumes on your basic disk. Only one of the four partitions allowed per physical disk can be an extended partition, and no primary partition needs to be present to create an extended partition. Extended partitions can be created only on basic disks. See also basic disk; logical drive; partition; primary partition.

FAT and FAT32

FAT and FAT32 are file systems that are defined as follows:

Fault tolerance

Ensures data integrity when hardware failures occur.

Free space

Available space used to create logical drives within an extended partition. See also extended partition; logical drive; unallocated space.

FT disk

Refers to a disk that is completely supported by Microsoft's Disk Administrator.

FT volume types

These are legacy systems that Array Manager can identify. These are basic volumes. You can use Disk Administrator in parallel with Array Manager if you need to keep these disks as basic disks.

Hot spare

A hot spare is an extra, unused disk that is part of a disk subsystem. It is assigned as a backup disk that can take over when a primary disk fails. Hot spares remain in standby mode, ready for activation in case of a disk failure. Hot spares can replace failed drives without interrupting the system or requiring user intervention.

Logical drive

A logical drive is a partition you create within an extended partition on a basic disk. A logical drive can be formatted and assigned a drive letter. Only basic disks can contain logical drives. A logical drive cannot span multiple disks. See also basic disk; basic volume; extended partition.

Mirrored volume (RAID-1)

A fault-tolerant volume that duplicates your data on two physical disks. It provides data redundancy by using a copy (mirror) of the volume to duplicate the information contained in the volume. The mirror is located on a different disk. If one of the physical disks fails, the data on the failed disk becomes unavailable, but the system continues to operate using the unaffected disk.

A mirrored volume is slower than a RAID-5 volume in read operations but faster in write operations. You can create mirrored volumes only on dynamic disks. You cannot extend mirrored volumes. In Windows NT 4.0 Disk Administrator, a mirrored volume is known as a mirror set. See also dynamic disk; dynamic volume; fault tolerance; RAID; volume.

NTFS

An advanced file system designed for use specifically within the Windows NT operating system. It supports file system recovery, extremely large storage media, long file names, and various features for the POSIX subsystem. It also supports object-oriented applications by treating all files as objects with user-defined and system-defined attributes. NTFS is also called Windows NT file system. See also FAT (File Allocation Table).

Parity

Redundant information that is associated with a block of information. In Array Manager software, parity is a calculated value used to reconstruct data after a failure.

RAID-5 volumes stripe data and parity intermittently across a set of disks. Within each stripe, the data on one disk is parity data and the data on the other disks is normal data. RAID-5 volumes therefore require at least three disks to allow for this extra parity information. When a disk fails, Array Manager software uses the parity information in those stripes in conjunction with the data on the good disks to recreate the data on the failed disk. See also fault tolerance; RAID-5 volume; striped volume.

Partition

A portion of a physical disk that functions as though it were a physically separate disk. Partitions can be created only on basic disks. Partitions cannot span disks; they must be a contiguous region. See also basic disk; extended partition; primary partition; system partition.

Physical array

A physical array is a collection of physical disk drives governed by RAID management software. A physical array appears to Array Manager as one or more logical drives.

Primary partition

A volume you create using unallocated space on a basic disk. Microsoft Windows NT and other operating systems can start from a primary partition. You can create up to four primary partitions on a basic disk, or three primary partitions and an extended partition. Primary partitions can be created only on basic disks and cannot be subpartitioned. See also basic disk; dynamic volume; extended partition; partition.

Providers

Providers run on a managed node along with the server on the Microsoft Windows NT 4.0 or Windows 2000 operating system. Providers are plug-ins to the server framework. Each provider is specific to the hardware controller or software component that the provider manages.

RAID

Hardware RAID (Redundant Array of Independent Disks) refers to:

RAID levels provide various mixes of performance, reliability, and cost. Array Manager supports the available RAID levels of the particular hardware included in your system.

Also, Array Manager supports three software RAID levels: Level 0 (striping), Level 1 (mirroring), and Level 5 (RAID-5). See also fault tolerance; mirrored volume; RAID-5 volume; striped volume.

RAID-5 volume (Stripe set with parity)

A RAID-5 volume is a fault-tolerant volume with data and parity striped intermittently across three or more physical disks. Parity is a calculated value that is used to reconstruct data after a failure. If a portion of a physical disk fails, you can recreate the data that was on the failed portion from the remaining data and parity. You can create RAID-5 volumes only on dynamic disks. You cannot mirror or extend RAID-5 volumes. In Windows NT 4.0 Disk Administrator, a RAID-5 volume is known as a striped set with parity. See also dynamic disk; dynamic volume; fault tolerance; parity; RAID; volume.

Region

Contiguous area of storage on a disk.

Simple volume

A volume that consists of contiguous space on a single disk. You can extend a simple volume within the same disk or onto additional disks. If you extend a simple volume across multiple disks or across noncontiguous areas on the same disk, it becomes a spanned volume. You can create simple volumes only on dynamic disks. Simple volumes are not fault tolerant but can be mirrored.

When a basic disk with a partition is upgraded, the partition becomes a simple volume. An extended partition on a basic disk also become a simple volume when the disk is upgraded to dynamic. See also dynamic disk; dynamic volume; fault tolerance; mirrored volume; spanned volume; volume.

S.M.A.R.T. (Self Monitoring Analysis and Reporting Technology)

This is a method of determining the reliability of an array disk by performing a predictive failure analysis on each disk, as defined by that disk's vendor. Array Manager picks up alerts sent from each RAID controller, if the hard disk supports S.M.A.R.T.

Spanned volume

A volume made up of disk space on more than one physical disk. A spanned volume can also consist of two or more noncontiguous areas on a single disk. You can add more space to a spanned volume by extending it at any time. You can create spanned volumes only on dynamic disks. Spanned volumes are not fault tolerant. In Windows NT 4.0 Disk Administrator, a spanned volume is known as a volume set. See also dynamic disk; dynamic volume; fault tolerance; mirrored volume; volume.

Striped volume (RAID-0)

A volume that stores data in stripes on two or more physical disks. Data in a striped volume is allocated alternately and evenly (in stripes) to the disks of the striped volume. You can create striped volumes only on dynamic disks. Striped volumes are not fault tolerant and cannot be mirrored or extended. In Windows NT 4.0 Disk Administrator, a striped volume is known as a stripe set. See also dynamic disk; dynamic volume; fault tolerant; volume.

System volume

The volume that has the hardware-specific files needed to load Windows NT/2000. See also volume; partition.

Subdisk

Refers to a region of contiguous space on a disk. Subdisks are building blocks for dynamic volumes.

Subsystem

Refers to all the objects on a particular array enclosure. It includes physical and logical objects.

Unallocated space

Available disk space that is not allocated to any partition, logical drive, or volume. The type of object you can create on unallocated space depends on the disk type (basic or dynamic). For basic disks, you can use unallocated space outside partitions to create primary or extended partitions. You can use free space inside an extended partition to create a logical drive. For dynamic disks, you can use unallocated space to create dynamic volumes. Unlike with basic disks, you do not select the exact disk region used to create the volume.

See also basic disk; dynamic disk; extended partition; logical drive; partition; primary partition; volume.

Virtual disk

A virtual disk is an abstract entity used by Array Manager that allows you to use different hardware RAID layouts on selected array disks. Virtual disks are hardware RAID logical drives. After the virtual disk is created and the system is rebooted, the virtual disk appears as a disk in Windows NT/2000. A virtual disk is functionally identical to a physical disk from the standpoint of applications.

Volume

A logical/virtual entity that is made up of portions of one or more physical disks. A volume may be formatted and may have a file system and/or drive letter. A volume has a type (dynamic) and a layout (simple, spanned, mirrored, striped, or RAID-5). See also dynamic volume; mirrored volume; RAID-5 volume; simple volume; spanned volume; striped volume.


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