Auto Assigned Addressing Option; Indexed Addressing Option - Dell PowerVault 35F User Manual

SCC Structures and Operation: Dell PowerVault 35F User's Guide
When the PowerVault 35F is configured to use SCC addressing, the unit is capable of responding as a controller
device to the FCP Initiator, or routing the FCP request to a specified BUS:TARGET:LUN triplet. When a request
using the Peripheral Device Addressing Method is received (An FCP command with the LUN field with bits 7 and 6 of
byte 0 are set to 0), the unit routes the request to the PowerVault 35F, which acts on the command directly. When a
request using the Logical Unit Addressing Method is received (bits 7 and 6 set to 10b), the request is routed to the
BUS:TARGET:LUN as specified in the defined field.
Host systems using SCC addressing will typically do initial device discovery using the Peripheral Device Addressing
method. On issuing an INQUIRY command, the host will receive the PowerVault 35F inquiry data
and Commands), indicating the device type as a controller device. The host will then know on this basis that
subsequent commands to attached devices will use the Logical Unit Addressing method. The host can perform
discovery by either walking through the BUS:TARGET:LUN values as would a standard SCSI driver, or by issuing a
REPORT LUNS command
the Peripheral Device Addressing Method), and returns a table indicating attached devices. The host can then perform
actions on these devices directly without having to perform discovery through all possible combinations.

Auto Assigned Addressing Option

The Auto Assigned option is similar to the Indexed addressing, but with the distinction that the table used is created
through SCSI device discovery on power up or reset, and not otherwise retained. As the unit performs device discovery
on a SCSI bus, the Index table relating FCP LUN values is filled with adjacent FCP LUNs referencing each
subsequent SCSI device. The host system will then detect every attached device without voids, allowing full device
discovery to the host. This allows easy configuration in environments where device ordering is not important and hot
plugging of SCSI devices will not occur. Tape libraries are excellent candidates for using Auto Assigned Addressing.
Configuration allows for discovery to be performed in order of bus, target, or LUN as desired for the specific
environment.

Indexed Addressing Option

Indexed Addressing allows for host bus adapter drivers that only use Peripheral Device addressing to access SCSI
devices attached to the PowerVault 35F unit. This is done by use of a table which is indexed by sequential LUN
values, indicating selected BUS:TARGET:LUN devices. It is not possible in this mode to address the PowerVault 35F
unit as a controller unit directly when using the Indexed Addressing option. The size of the table is equal to the number
of busses times the number of targets per bus, less one initiator ID per bus, times the number of LUNs per target. The
index table can be manually edited. Configuration tools allow for the table to be filled in order of increasing bus,
target, or LUN, as may be desired for the specific requirements needed. A method is also provided to perform device
discovery, and fill the table in the order that devices are discovered on the SCSI busses. As an example, if there are
three devices connected to a SCSI bus at BUS:TARGET:LUN 0:0:0, 0:1:0 and 0:2:0, The Indexed table will look like
Table 6.
NOTE: The "–" indicates a null entry.
Table 6. Example of Fibre Channel-to-SCSI mapping table
FC_LUN
0x00
0x01
0x02
file:///C|/Users/rishi_sood/Desktop/35F/ug/scc_addr.htm[3/21/2013 11:16:24 AM]
(Fibre Channel Interface and
BUS TGT LUN
0 0 0
0 1 0
0 2 0
Commands). This command is sent to the controller (using
(SCSI Interface