Product manual

231
Chapter 7: Technology Background
This chapter covers the following topics:
• Introduction to RAID (below)
• Choosing a RAID Level (page 242)
• Choosing Stripe Size (page 245)
• Choosing Sector Size (page 245)
• Cache Policy (page 246)
• Cache Mirroring (page 248)
• LUN Affinity (page 249)
• Capacity Coercion (page 250)
• Initialization (page 251)
• Hot Spare Drive(s) (page 251)
• Partition and Format the Logical Drive (page 252)
• RAID Level Migration (page 252)
• Media Patrol (page 255)
• Predictive Data Migration (PDM) (page 256)
• Transition (page 257)
Introduction to RAID
RAID (Redundant Array of Independent Disks) allows multiple hard 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/or controller handle
all of the individual drives on its own. 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 disk arrays use different organizational models and have
varying benefits. Also see “Choosing a RAID Level” on page 242. The following
outline breaks down the properties for each type of RAID disk array: