Users guide

Intel® RAID Software User Guide 32
a time) during boot. With a RAID-level migration running, a boot can often take more
than 15 minutes.
3.4.1 Drive Hierarchy within the RAID Firmware
The Intel
®
Integrated RAID firmware is based on three fundamental levels. Virtual drives
are created from drive arrays that are created from physical drives.
• Level 1 consists of the physical drives (hard drives and removable hard disks). The
firmware identifies each drive by its physical ID and maps it to a virtual address. A
virtual drive can be constructed of more than one physical drive.
• Level 2 consists of the array(s) formed by firmware made of one or more disks and
can be made into RAID 0, 1, 5, 6, 10, 50, or 60.
• Level 3 consists of the virtual drives. These are the only drives that can be accessed
by the operating system. These are the drives given drive letters (C, D, and so forth)
under the Microsoft Windows* operating system. The firmware automatically
transforms each newly installed drive array into a virtual drive. RAID 0, 1, 5, or 6
use a single array and RAID 10, 50, 60 use multiple arrays.
3.5 Intel
®
Intelligent RAID Controller Features
3.5.1 Enterprise Features
• Online capacity expansion (OCE). Add capacity to the virtual drive. The added
capacity can be presented to the operating system as additional space for the
operating system to partition it as an additional drive, or it may be added to an
operating system drive, depending upon the capability of the operating system.
• Online RAID level migration allows for upgrading a RAID level. Options are to go
from RAID 1 to RAID 0, RAID 5 to RAID 0, RAID 6 to RAID 0, RAID 6 to RAID
5. With OCE, options are to go from RAID 0 to RAID 1, RAID 0 to RAID 5, RAID
0 to RAID 6, RAID 1 to RAID 5, RAID 1 to RAID 6, RAID 5 to RAID 6.
— You cannot migrate or perform OCE on a sp
anned RAID array or disk group
(RAID 10, RAID 50, or RAID 60).
— You cannot migrate to a smaller capacity configuration.
— You cannot perform OCE when there is more than one virtual drive on a
virtua
l array or disk group.
• Each controller allows 128 virtual drives.
• When five or more disks are used, Smart Initialization automatically checks
consistency of virtual drives for RAID 5. This allows performance optimization by
enabling read-modify-write mode of operation with five or more disks in a RAID 5
array or disk group. Peer read mode of operation is used when the RAID 5 array or
disk group contains three or four physical drives.