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volume set can consume all or a portion of the available disk capacity in a RAID set. Multiple volume sets can exist in
a RAID set. For the RAID controller, a volume set must be created either on an existing RAID set or on a group of
available individual disks (disks that are about to become part of a RAID set). If there are pre-existing RAID sets with
available capacity and enough disks for the desired RAID level, then the volume set can be created in the existing
RAID set of the user's choice.
In the illustration, volume 1 can be assigned a RAID level 5 of operation while volume 0 might be assigned a RAID
level 1E of operation. Alternatively, the free space can be used to create volume 2, which could then be set to use
RAID level 5.
Ease of Use Features
Foreground Availability/Background Initialization
•
RAID 0 and RAID 1 volume sets can be used immediately after creation because they do not create parity
data. However, RAID 3, 5, 6, 30, 50 or 60 volume sets must be initialized to generate parity information. In
Background Initialization, the initialization proceeds as a background task, and the volume set is fully
accessible for system reads and writes. The operating system can instantly access the newly created arrays
without requiring a reboot and without waiting for initialization to complete. Furthermore, the volume set is
protected against disk failures while initialing. If using Foreground Initialization, the initialization process
must be completed before the volume set is ready for system accesses.
Online Array Roaming
•
RAID controllers store RAID configuration information on the disk drives. The controller therefore protects
the configuration settings in the event of controller failure. Online array roaming allows the administrators
the ability to move a complete RAID set to another system without losing RAID configuration information or
data on that RAID set. Therefore, if a server fails, the RAID set disk drives can be moved to another server
with an Sans Digital RAID controllers and the disks can be inserted in any order.
Online Capacity Expansion
•
Online Capacity Expansion makes it possible to add one or more physical drives to a volume set without
interrupting server operation, eliminating the need to backup and restore after reconfiguration of the RAID
set. When disks are added to a RAID set, unused capacity is added to the end of the RAID set. Then, data on
the existing volume sets (residing on the newly expanded RAID set) is redistributed evenly across all the
disks. A contiguous block of unused capacity is made available on the RAID set. The unused capacity can be
used to create additional volume sets.
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