Users guide

25 Intel® RAID Software User Guide
— If you add a hot spare (assume a global hot spare) during a copyback
operation, the copyback is aborted, and the rebuild operation starts on the hot
spare.
2.4.6 Configuration Planning
Factors to consider when planning a configuration are the number of physical disks the
RAID controller can support, the purpose of the array, and the availability of spare drives.
Each type of data stored in the disk subsystem has a different frequency of read and write
activity. If you know the data access requirements, you can more successfully determine a
strategy for optimizing the disk subsystem capacity, availability, and performance.
Servers that support video-on-demand typically read the data often, but write data
infrequently. Both the read and write operations tend to be long. Data stored on a general-
purpose file server involves relatively short read and write operations with relatively small
files.
2.4.7 Dimmer Switch Feature
Powering and cooling drives represents a major cost for data centers. The new MegaRAID
Dimmer™ Switch reduces the power consumption of the devices connected to a
MegaRAID controller. This helps to share resources more efficiently and lower costs.
With Dimmer Switch, any unconfigured drive connected to a MegaRAID controller is
spun down after 30 minutes of inactivity, reducing its power usage. Spun down drives are
spun up automatically when you create a configuration using those drives.
2.4.8 Serial ATA III Features
The SATA bus is a high-speed, internal bus that provides a low pin count (LPC), low
voltage level bus for device connections between a host controller and a SATA device.
The following list describes the SATA III features of the RAID controllers:
• Supports SATA III data transfers of 12Gb/s
• Supports STP data transfers of 12Gb/s
• Provides a serial, point-to-point storage interface
• Simplifies cabling between devices
• Eliminates the master-slave construction used in parallel ATA
• Allows addressing of multiple SATA II targets through an expander
• Allows multiple initiators to address a single target (in a fail-over configuration)
through an expander