Promise Technology EX8650A, EX4650A user manual Technology Background, Introduction to RAID

Chapter 6: Technology Background

•Introduction to RAID (below)

•Choosing a RAID Level (page 168)

•Choosing Stripe Block Size (page 172)

•Choosing Sector Size (page 172)

•Choosing Cache Policy (page 173)

•Capacity Coercion (page 174)

•Initialization (page 175)

•Hot Spare Drive(s) (page 175)

•Partition and Format the Logical Drive (page 176)

•RAID Level Migration (page 176)

•Media Patrol (page 184)

•Predictive Data Migration (PDM) (page 184)

•Transition (page 185)

•Critical & Offline Logical Drives (page 189)

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 168. The following outline breaks down the properties for each type of RAID logical drive:

155