Compaq External RAID Controller & Subsystem Infortrend, Руководство по эксплуатации

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RAID Planning
2-7
2.3 Operation Theory
2.3.1 I/O Channel, SCSI ID, and LUN
Depending on the interface used by a RAID system, a SCSI drive
channel (SCSI bus) can connect up to 15 drives (excluding the RAID
controller itself). A Fibre channel 125 drives in a loop. Each device
occupies one unique ID.
Figure 2 - 3 SCSI ID/LUNs
The figure on the left illustrates the idea of mapping a system
drive to host ID/LUN combinations. The host ID is like a
cabinet, and the drawers are the LUNs (LUN is short for Logical
Unit Number). Each cabinet (host ID) can have up to 32
drawers (LUNs). Data can be made available through one of the
LUNs of a host ID. Most host adapters treat a LUN like another
device.
2.3.2 Grouping Drives into an Array
Figure 2 - 4 Connecting Drives
The physical connection of a RAID controller should be similar to
the one shown above. Drives are connected through I/O paths that
have been designated as drive channels.
The next diagram shows two logical configurations of drives and the
physical locations of its members. Using drives from different
channels can lower the risk of fatal failure if one of the drive
channels should fail. There is no limitation on the locations of
spares.