Understanding Raid Concepts; What Is Raid - Dell iDRAC 8 User Manual

PERC Capability
Real-time
Staged
Related links

Understanding RAID concepts

Inventorying and monitoring storage devices
Viewing storage device topology
Managing controllers
Managing physical disks
Managing enclosures or backplanes
Managing PCIe SSDs
Managing virtual disks
Blinking or unblinking component LEDs
Supported controllers
Supported enclosures
Summary of supported features for storage devices
Understanding RAID concepts
Storage Management uses the Redundant Array of Independent Disks (RAID) technology to provide Storage Management
capability. Understanding Storage Management requires an understanding of RAID concepts, as well as some familiarity with how
the RAID controllers and operating system view disk space on your system.

What is RAID?

RAID is a technology for managing the storage of data on the physical disks that reside or are attached to the system. A key aspect
of RAID is the ability to span physical disks so that the combined storage capacity of multiple physical disks can be treated as a
single, extended disk space. Another key aspect of RAID is the ability to maintain redundant data which can be used to restore data
in the event of a disk failure. RAID uses different techniques, such as striping, mirroring, and parity, to store and reconstruct data.
There are different RAID levels that use different methods for storing and reconstructing data. The RAID levels have different
characteristics in terms of read/write performance, data protection, and storage capacity. Not all RAID levels maintain redundant
data, which means for some RAID levels lost data cannot be restored. The RAID level you choose depends on whether your priority
is performance, protection, or storage capacity.
NOTE: The RAID Advisory Board (RAB) defines the specifications used to implement RAID. Although RAB defines the
RAID levels, commercial implementation of RAID levels by different vendors may vary from the actual RAID
specifications. An implementation of a particular vendor may affect the read and write performance and the degree of
data redundancy.
Hardware and software RAID
RAID can be implemented with either hardware or software. A system using hardware RAID has a RAID controller that implements
the RAID levels and processes data reads and writes to the physical disks. When using software RAID provided by the operating
CEM configuration Capable Controller
(PERC 9.1 or later)
If there is no existing pending or
scheduled jobs for the controller, then
configuration is applied.
If there are pending or scheduled jobs for
that controller, then the jobs have to be
cleared or you must wait for the jobs to be
completed before applying the
configuration at run-time. Run-time or
real-time means, a reboot is not required.
If all the set operations are staged, the
configuration is staged and applied after
reboot or it is applied at real-time.
CEM configuration Non-capable
Controller (PERC 9.0 and lower)
Configuration is applied. An error message
is displayed. Job creation is not successful
and you cannot create real-time jobs using
Web interface.
Configuration is applied after reboot
183