Before you can use global-active device on your storage systems, you must ensure that system requirements, configurations, power and physical cabling, memory requirements, cache requirements, host modes, and system operation modes are configured appropriately.
To prepare the storage systems for global-active device operations:
- Make sure that the primary, secondary, and external storage systems meet the global-active device system requirements described in chapter 2.
- Make sure that the primary storage system is configured to report sense information to the host. The secondary storage system should also be attached to a host server to report sense information in the event of a problem with an S-VOL or the secondary storage system.
- If power sequence control cables are used, set the power source selection switch for the cluster to "Local" to prevent the server from cutting the power supply to the primary storage system. In addition, make sure that the secondary storage system is not powered off during GAD operations.
- Establish the physical paths between the primary and secondary storage systems. Switches and channel extenders can be used. For details, see Planning physical paths.
- Review the shared memory requirements
for the primary and secondary storage systems in Requirements and restrictions. Make sure that the cache in both
storage systems works normally. Pairs cannot be created if cache requires
maintenance.
Configure the cache on the secondary storage system so that it can adequately support the remote copy workload and all local workload activity. When the cache memory and the shared memory in the storage system become redundant, you can remove them. For instructions on adding and removing cache and shared memory, see Adding and removing shared memory.
- Make sure that the appropriate host modes and host mode options (HMOs) are set. For details, see the
Provisioning Guide for the storage system.
- HMO 78, the nonpreferred path option, must be configured to specify nonpreferred paths for HDLM operations.
- HMOs 49, 50, and 51 can be used to improve response time of host I/O for distance direct connections (up to 10 km Long Wave).
- Make sure that the appropriate system option modes (SOMs) are set on your storage systems. For a list of SOMs, see the System Administrator Guide. For details about SOMs that apply to remote copy operations, contact customer support.