Disk Array Terms - Promise Technology FastTRAK66 User Manual

Disk Array Description
A "disk array" is formed from a group of 2 or more disk drives which appear to the
system as a single drive. The advantage of an array is to provide better throughput
performance and/or data fault tolerance. Better performance is accomplished by
sharing the workload in parallel among multiple physical drives. Fault tolerance is
achieved through data redundant operation where if one (or more) drive fails or has
a sector failure, a mirrored copy of the data can be found on another drive(s).
For optimal results, select identical Ultra ATA/66 drives to install in disk arrays. The
drives' matched performance allows the array to function better as a single drive.
Disk Array Member
The individual disk drives in an array are called "members." Each member of a
specific disk array is coded in their "reserved sector" with configuration information
that identifies the drive as a member.
Disk Array Types
For most installations, the FastBuild
your system.
There are four disk array types in three categories that can be installed on the
FastTrak66 card. Striping is in the Performance category while Mirroring, Striping/
Mirroring are in the Fault Tolerance category. Spanning (JBOD) is in the Capacity
category.
Disk arrays within the Performance and Fault Tolerance categories conform with the
Redundant Array of Independent Disks technology, or RAID. The RAID levels
supported are 0, 1, and 0/1.
RAID Level
RAID 0 (Striping)
RAID 1 (Mirroring)
RAID 0+1 (Stripe/Mirror)
JBOD (Spanning)
All disk members in a formed disk array are recognized as a single physical drive to
the system.
Understanding Disk Array Concepts
Disk Array T erms
TM
Read/Write
Performance
Best/Best
High /Normal
Best/High
Normal/Normal
setup "<1> Auto Setup" option will configure
Redundancy
Capacity
50% min
50% min
Number
of Drives
- - -
2 to 4
- - -
2 to 4
2
4
6-2