BC4000 Series RAID Controllers
User Manual
02/13/06
B ro ad c om C o r p or at i on
Page 2
Overview of RAID Concepts
Document
BC4000-UM100-R
S e c t i o n 2 : O v e r v i ew o f R A I D Co n c e p t s
U
NDERSTANDING
A
RRAYS
Disk arrays are several disks that are grouped together in various organizations to improve either the
performance or the reliability of a computer’s storage system. Because some array types enhance
performance while others improve reliability, and because some array types enhance both, it is important to
consider your needs when planning an array configuration.
The BC4000 Series RAID controller supports various array types. For small systems with four or less drives,
RAID1 and RAID5 are appropriate choices. For larger systems with more drives available, RAID10 and
RAID50 may be the appropriate choices. The unique ability of the RAIDCore controller to provide online
expansion to other array types such as RAID10 and RAID50 across multiple drives and controllers becomes
extremely valuable when expanding storage is a requirement.
O
VERVIEW
OF
A
RRAY
T
YPES
The BC4000 Series RAID controller supports the following Redundant Array of Independent Disk (RAID) array
types. Note that the list of supported array types is affected by a controller’s license level.
•
Volume
: The controller treats one or more disks or unused space on a disk as a single array. Volume
provides the ability to concatenate storage from various drives regardless of the size of the space on
those drives. Volume is useful in scavenging space on drives unused by other arrays. Volume does not
provide any performance or data redundancy benefit.
•
RAID0
: RAID0, or striping, provides the highest performance but no data redundancy. Data in the array is
striped (distributed) across several physical drives. RAID0 arrays are useful for holding information such
as the operating system paging file, where performance is extremely important but redundancy is not.
•
RAID1
: RAID1, or mirroring, mirrors data on a partition of one disk to another. RAID1 is useful when there
are only two disks available and data integrity is more important than storage capacity.
•
RAID1n
: RAID1n, or n-way mirroring, mirrors the data stored in one hard drive to several hard drives. This
array type provides superior data redundancy because there are three or more copies of the data, and is
useful for creating exact copies of an array for backup purposes. However, this array type is expensive, in
both performance and the amount of disk space necessary to create the array type.
•
RAID10
: RAID10 is also known as RAID(0+1) or striped mirror sets. This array type combines mirrors and
stripe sets. RAID10 allows multiple drive failures, up to 1 failure in each mirror that has been striped. This
array type offers better performance than a simple mirror because of the extra drives. RAID10 requires
twice the disk space of RAID0 to offer redundancy.
•
RAID10n
: RAID10n stripes multiple n-way mirror sets. RAID10n allows multiple drive failures per mirror
set, up to n-1 failures in each mirror set that has been striped, where n is the number of drives in each
mirror set. This array type is useful in creating exact copies of an array's data using the split command.
This array type offers better random read performance than a RAID10 array, but uses more disk space.
Note:
It is highly recommended that you review this documentation in its entirety before configuring
arrays. Some of the advanced features of this controller (such as Online Capacity Expansion,
Online RAID Level Migration, sparing options) need to be understood by the user before arrays are
created.
