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

When replicating with Unisys SafeGuard Solutions, the RAs must be
able to send I/O to these storage devices, even if they are reserved by
some other initiator. The only way for the RA to reach the target
storage is through a virtual target, and from there (to the target
storage) by way of a virtual initiator. The RA cannot, however, use an
existing virtual target to access the storage target, since each virtual
target can use more than one virtual initiator to access the backend
device, and each RA port accessing the virtual target must be bound
to a single virtual initiator.
Therefore, the RA uses a special virtual target, called an appliance
virtual target (AVT) to enable it to access the storage target.
Whenever you specify (in the Unisys SafeGuard Solutions
Management Application or CLI) that a group side supports
reservations, the Unisys SafeGuard Solutions SAS agent creates one
AVT for each virtual initiator that represents a host initiator that has
access to volumes within this group. For every LUN that the initiator
may reserve, a corresponding LUN that points to the same physical
storage LUN is created on the AVT.
Because a single initiator may access LUNs on more than one storage
target, the LUNs on the AVT may represent as many different storage
targets as the number of storage targets on which the corresponding
initiator can reserve LUNs. Also, all LUNs on the AVT are created in
pass-through mode, so that I/Os sent to the AVT LUNs are not split
(which would cause the I/Os to be sent back to the RA), but rather,
are written directly to the storage target. Access to the AVT is limited
so that only RA ports can access the LUNs on the AVT.
When replicating a group that supports reservations, if the regular
path to the target storage device returns a “Reservation conflict”
error, the RA then checks other potential paths, including the AVTs.
Since the RA cannot determine which host initiator is reserving the
device, all existing AVTs are tried until one is found that allows access
to the target storage.
A list of 200 PWWNs is produced during installation of the Unisys
SafeGuard Solutions SAS agent, and is placed in the file
/thirdparty/recoverpoint/init_host/scimitar_wwns_list.txt on the
BP module. The WWNs are unique for the switch. They are available
for subsequent use by AVTs.
The RA port must have access to the virtual target, so zoning must be
set correctly according to the specification listed in “Zoning” on
page 12. All of the WWNs from the scimitar_wwns_list.txt file should
be zoned as AVTs.
16 Unisys SafeGuard Solutions Deploying Brocade AP-7600B and PB-48K-AP4-18 Devices Technical Notes