SafeGuard Solutions Deploying Brocade AP-7600B and PB-48K ...

Using dual DPCs in
frame redirect
mode
When working in frame redirect mode with the Unisys SafeGuard
Solutions SAS agent for Unisys SafeGuard Solutions 6.1, the agent
utilizes both DPCs by alternating the DPC on which it creates each
new virtual target. Since virtual initiators and virtual targets that
reside on different DPCs cannot interact, then if a single initiator is
bound to targets on both DPCs, it will be necessary to represent that
initiator with a separate VI on each DPC. A target, however, is always
represented by a single VT.
For example, if initiator I1 is bound to target T1 and initiator I2 is
bound to Target T2, the Unisys SafeGuard Solutions SAS agent
creates VI1 and VT1 on DPC 0 and VI2 and VT2 on DPC 1. If I1 is
bound also to T2, the agent must create another VI for I1 on DPC
1—since VI1, that resides on DPC #0 cannot interact with VT2 on
DPC 1. When enabling reservation support for a group, the agent will
create an AVT for each VI that represents a host that has access to a
volume that supports reservations, up to one AVT per initiator per
DPC.
Although the total number of virtual entities may be higher when
utilizing two DPCs, the number of virtual entities per DPC is always
lower. Hence, the possible scalability in this mode is always higher
(since the limit is per DPC). The number of used ITLs is not affected
by the utilization of both DPCs, but the maximum possible number of
ITLs doubles, as does the number of virtual initiators.
To determine the number of virtual entities on each DPC, use the 4-bit
DPC number in the WWN to determine the DPC number of each VT
(as described under “Virtual target WWNs”). Then, use the binding
scheme to determine the number of VIs for each DPC. Note that an
additional VI (the “System VI”) will be created on DPC 0.
Note: Dual DPC utilization is not supported for multi-VI mode.
10 Unisys SafeGuard Solutions Deploying Brocade AP-7600B and PB-48K-AP4-18 Devices Technical Notes