Data Replication Manager Windows-Based Server with Single Host Bus Adapter - Application Notes

Additional Considerations
12 Application Notes – Data Replication Manager Windows-Based Server with Single Host Bus Adapter
Failure of Intersite Link (ISL)
If the ISL is lost, the behavior of the total solution depends on the actual configuration of the local
HSG80 controller. There are three possible configurations:
• REMOTE COPY SET ERROR_MODE=NORMAL
— Association Set With Logdisk: The units remain operational on the current controllers and
operation continues. When the ISL is restored, only the updates as of the moment of ISL
failure will be sent to the remote site. However, if the logdisk is full, a full copy will occur.
— Association Set Without Logdisk: The units remain operational on the current controllers
and operation continues. When the ISL is restored, a full copy is initiated to the remote site.
• REMOTE COPY SET ERROR_MODE=FAILSAFE
— Association Set Without Logdisk: Access to the units is frozen during the failsafe_locked
state. If you are running Windows, you will see many errors, indicating that the device is no
longer reachable. You can exit the failsafe_locked state by entering the following CLI
command for every remote copy set belonging to the initiator unit that is in failsafe_locked
state:
SET RemoteCopySetName ERROR_MODE = NORMAL
When the ISL is restored, a full copy is initiated to the remote site. After the remote site is
fully synchronized, enter the following CLI command for all relevant remote copy sets:
SET RemoteCopySetName ERROR_MODE = FAILSAFE
Additional Considerations
Storage Area Network (SAN) Management
In all DRM configurations, and in single FC HBA configurations in particular, it is very important to
monitor all components in the SAN and to receive notification as soon as a component fails. Timely
fault notification enables you to undertake action quickly to reduce the downtime caused by the failed
component.
Elements to be monitored include Fibre Channel switches, HSG80 controllers and, if applicable, other
equipment such as FC-ATM gateways. All equipment, except the HSG80, is capable of sending simple
network management protocol (SNMP) traps to several destinations for fault notification. The FC
switches detect and report via SNMP any failures of GBICs, fiber optic cables (including intersite
links), and power supplies within the FC switches.
Failures within the storage subsystem can be detected and reported by either the SWCC agent or the
HSG Element Manager installed on a SANworks Management Appliance.
Multiple Switches in the FC Fabric
In larger configurations, the number of ports on an FC switch may not be sufficient for the connection
of multiple HSG80 controllers, the intersite links, and the servers. In this case, you can build any
supported FC switch fabric, but keep in mind that it must conform to the rules given in the SANworks
Data Replication Manager by Compaq Application Notes - HSG80 ACS Version 8.6-4P Design Guide
and the Compaq StorageWorks Heterogeneous Open SAN Design Reference Guide.
Pay special attention to the following DRM restrictions:
• Number of hops between the server and the host port 1 of the HSG80s.