Virtual Disk Layouts

This module provides short descriptions of the virtual disk layouts, or hardware RAID levels, supported for viewing in Server Administrator.

The following hardware RAID levels are supported for viewing in Server Administrator:

Concatenation

Concatenation refers to storing data on either one array disk or on disk space that spans multiple array disks. When spanning more than one disk, concatenation enables the operating system to view multiple array disks as a single disk.

RAID 0 (Striped)

A volume created by combining areas of free space on two or more disks into one logical volume. Data is divided into blocks and spread in a fixed order among all the disks in the volume. With a striped volume, data is written to multiple disks, similar to spanned volumes. However, striping writes files across all disks so that data is added to all disks at the same rate.

Striped volumes offer the best performance of all the disk management strategies. However, striped volumes do not provide fault tolerance. If a disk in a striped volume fails, the data in the entire volume is lost. You cannot mirror or extend a striped volume.

RAID 1 (Mirrored)

A fault-tolerant volume that duplicates data on two physical disks. A mirror provides redundancy by simultaneously writing the same data onto two separate volumes that reside on different disks. If one of the disks fails, data continues to be written to and read from the unaffected disk. You can mirror only a simple or spanned dynamic volume.

RAID 5 (Striping with distributed parity)

A fault-tolerant volume with data and parity striped alternately across three or more physical disks. Parity is a calculated value that is used to reconstruct data after a failure. If one of the physical disks fails, data that was on the failed disk is re-created from the remaining data and parity on the other disks. RAID-5 volumes are a good solution for data redundancy in a computer environment in which most activity consists of reading data.

You need a minimum of three disks for a RAID 5 volume.

RAID 10 (Striping over mirrored sets)

A variation of RAID 1 that combines data striping and mirroring. RAID 10 combines mirrored drives (RAID 1) with data striping (RAID 0). With RAID 10, data is striped across multiple drives. The set of striped drives is then mirrored onto another set of drives. RAID 10 can be considered a mirror of stripes.

RAID 50 (Concatenated distributed parity)

RAID 50 is a concatenation of RAID 5 across more than one three-drive spans. For example, a RAID 5 array that is implemented with three drives and then continues on with three more array drives would be a RAID 50 array.

Concatenation refers to storing data on either one array disk or on disk space that spans multiple array disks. When spanning more than one disk, concatenation enables the operating system to view multiple array disks as a single disk.

Because concatenated volumes do not use disk space to maintain redundant data, they are more cost-efficient than volumes that use mirrors or parity information. A concatenated volume may be a good choice for data that is temporary, easily reproduced, or that does not justify the cost of data redundancy. In addition, a concatenated volume can easily be expanded by adding an additional array disk.

RAID 1 Concatenated (Concatenated mirror)

RAID 1 Concatenated is a RAID 1 array that spans across more than a single pair of array disks. This combines the advantages of concatenation with the redundancy of RAID 1. No striping is involved in this RAID type.

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