HP Array Controller HSG V8.7 Software - Manual (Page 114)

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In Figure 3–15, the controller addresses DISK30800 through device
port 3, target 08, LUN 00. This PTL location indicates the pathway the
controller uses to address a disk drive (device) in the subsystem. It also
indicates the device name.
The controller uses the PTL location to name each device that you add
to your subsystem with StorageWorks Command Console or the
CONFIG utility. (Factory-installed devices are added with the CONFIG
utility. Thus, their names derive from their PTL locations.) For
example, if the controller finds a disk in PTL 10200, it names it
DISK10200.
When your controller receives an I/O request, it identifies the storageset
unit number for the request, then correlates the unit number to the
storageset name. From the storageset name, the controller locates the
appropriate device for the I/O request. (For example, the RAIDset
“RAID1” might contain DISK10000, DISK20000, and DISK30000.)
The controller generates the read or write request to the appropriate
device using the PTL addressing convention. Figure 3–16 illustrates the
concept of PTL addressing.
Figure 3–16 Locating Devices using PTLs
D100
RAID1
Disk 10000 Disk 20000 Disk 30000
Storageset
name
Host addressable
unit number
Controller
PTL addresses
CXO6186A