Table of Contents
Advertisement
MaxAttach NAS 6000 Administration Guide
The user data arrays in the Maxtor MaxAttach NAS 6000 Base Unit are factory configured
as RAID 5 arrays, or although RAID 0 or RAID 1 arrays may be used along with another
common disk drive configuration method called JBOD (Just a Bunch of Disks).
Key RAID Technical Methods
These key technical methods are used in varying combinations in most RAID/JBOD
configurations and will help you understand how a disk array works and why you want one
type as opposed to another type for your application.
Hardware RAID and Software RAID
RAID is also divided by the way it is implemented. In the MaxAttach, the disk arrays are
implemented as "Hardware RAID" and controlled by a RAID Controller card located in
the system Base Unit. In some systems, software drivers are used to control RAIDs or
"Software RAID."
In hardware RAID, an array of disk drives is controlled by a RAID controller which
administers the data I/O to the disks based on the type of RAID configuration. Using
today's disk drives, RAID controllers use combinations of striping, spanning, mirroring and
parity checking techniques to obtain an optimum balance of increased disk size, improved
data safety, and increased read/write I/O performance.
Striping
Striping is the underlying concept behind most RAID levels. A stripe is a contiguous
sequence of data blocks that is written to one or more disk drives. A stripe may be as short
as a single data block, or may consist of thousands. The RAID controllers split up their
component disk partitions into stripes; the different RAID levels differ in how they
organize the stripes, and what data they put in them. The interplay between the size of the
stripes, the typical size of files in the file system, and their location on the disk is what
determines the overall performance of the RAID subsystem. The effect is to allow larger
data volumes than those provided by a single physical disk. Striping is also called Spanning.
Mirroring
Mirroring is creating an exact copy of data from one drive or array on a second drive or
array. The entire read/write procedure is done in parallel. Mirroring is the highest level of
fault tolerance with 100% of the data backed up as it is created and written. Mirroring is
also the most expansive fault tolerance technique where 50% of you disk space is spent on
providing fault tolerance,
Chapter #11 - Appendix - Disk Array RAID Concepts
11/07/01 -- Revision 2.0.03A
Chapter #11 - Appendix - Disk Array RAID Concepts
256
Key RAID Technical Methods
000001628
Advertisement
Table of Contents
