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Chapter 9: Technology Background
This chapter covers the following topics:
•
Introduction to RAID (below)
•
Choosing a RAID Level (page 332)
•
Choosing Stripe Size (page 336)
•
Choosing Sector Size (page 336)
•
Cache Policy (page 337)
•
Capacity Coercion (page 339)
•
Initialization (page 340)
•
Hot Spare Drive(s) (page 340)
•
Partition and Format the Logical Drive (page 341)
•
RAID Level Migration (page 341)
•
Media Patrol (page 350)
•
Predictive Data Migration (PDM) (page 351)
•
Transition (page 352)
Introduction to RAID
RAID (Redundant Array of Independent Disks) allows multiple physical drives to
be combined together in a disk array. Then all or a portion of the disk array is
formed into a logical drive. The operating system sees the logical drive as a
single storage device, and treats it as such.
The RAID software and controller manage all of the individual drives. The
benefits of a RAID can include:
•
Higher data transfer rates for increased server performance
•
Increased overall storage capacity for a single drive designation (such as, C,
D, E, etc.)
•
Data redundancy/fault tolerance for ensuring continuous system operation in
the event of a hard drive failure
Different types of logical drives use different organizational models and have
varying benefits. Also see ―Choosing a RAID Level‖ on page 332. The following
outline breaks down the properties for each type of RAID logical drive:
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