RAID Levels and Data Protection

Redundant Array of Independent Disks (RAID) describes a storage solution in which part of the storage capacity stores redundant information about user data that is stored on the remainder of the storage capacity. The redundant information enables regeneration of user data if one of the disk drives in the fails.

RAID relies on a series of configurations, called levels, to determine how user and data is written and retrieved from the disk drives.

RAID Level 1, RAID Level 3, RAID Level 5, and RAID Level 6 write redundancy data to the disk drive media for fault tolerance. The redundancy data might be a copy of the data (mirrored) or an error-correcting code derived from the data. You can use the redundancy data to quickly reconstruct information on a replacement disk drive if a disk drive fails.

You configure a single RAID level across a single array. All redundancy data for that array is stored within the array. The capacity of the array is the aggregate capacity of the member disk drives minus the capacity reserved for redundancy data. The amount of capacity needed for redundancy depends on the RAID level used. Select Array >> Change >> RAID Level when you want to change the redundancy of the array, such as changing from RAID Level 1 to RAID Level 5 .

This storage management software offers the following RAID level configurations: RAID Level  0, RAID Level  1 or RAID Level  10, RAID Level  3, RAID Level  5, and RAID Level 6. These RAID levels are described in the sections that follow. Each RAID level also provides different performance features. For more information about performance, refer to the RAID Levels and Performance online help topic.

RAID Level 0

Short description – Non-redundant, striping mode.

How it works – RAID Level 0 stripes data across all of the disk drives in the array.

Data protection features

Disk drive number requirements – RAID Level 0 arrays can have more than 30 disk drives. You can create an array that includes all of the disk drives in the storage subsystem.

RAID Level 1 or RAID Level 10

Short description – Striping/mirror mode.

How it works

Data protection features

Disk drive number requirements

RAID Level 3

Short description – High bandwidth mode.

How it works

Data protection features

Disk drive number requirements

RAID Level 5

Short description – High I/O mode.

How it works

Data protection features

Disk drive number requirements

RAID Level 6

Short description – High I/O mode.

How it works

Data protection features

Disk drive number requirements


Note:

RAID Level 6 is available only to those controllers that are capable of supporting the P+Q calculation. The model DS4800 (Models 82, 84, 88) controller is not supported, however, the model DS4700 Model 70 controller and the model DS4700 Model 72 controller are supported. A premium feature key allows customers to use RAID Level 6 and to use Dynamic RAID-Level Migration (DRM).

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