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Chapter 3
3. Features of the RAID Controller
This chapter describes features and operation of the RAID controller in the following
sections:
• “Enclosure Services Interface (ESI) and Disk Drive Control” on page 47
• “Configuration on Disk (COD)” on page 48
• “Drive Roaming” on page 49
• “Data Caching” on page 50
• “RAID Disk Topologies” on page 52
Enclosure Services Interface (ESI) and Disk Drive Control
Both the JOBD and RAID LRC I/O modules use enclosure services interface (ESI)
commands to manage the physical storage system. ESI provides support for disk drives,
power supply, temperature, door lock, alarms, and the controller electronics for the
enclosure services. The storage system ESI/ops panel firmware includes SES.
Note: These services are performed by drives installed in bays 1/1 and 4/4; these drives
must be present for the system to function. See Figure 1-17 on page 23 for diagrams of
their location.
ESI is accessed through an enclosure services device, which is included in the ESI/ops
module. SCSI commands are sent to a direct access storage device (namely, the drives in
bays 1/4 and 4/4), and are passed through to the SES device.
During controller initialization, each device attached to each loop is interrogated, and the
inquiry data is stored in controller RAM. If ESI devices are detected, the ESI process is
started. The ESI process polls and updates the following data:
• Disk drive insertion status
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