When adding an external path, verify if a different path uses the same route. The following table describes whether to add an external path to a route being used for a different path.
| External storage system | Whether to add an external path to a route being used | Restriction |
|---|---|---|
| Hitachi | An external path can be added to a route being used for the following paths:
|
The operations listed in the following table might cause a path being used to be temporarily disconnected (however, the path being used is not blocked because of the immediate reconnection). Therefore, the host I/O performances or the remote copy performances for the external volumes might be temporarily degraded. |
| Non-Hitachi | An external path cannot be added to a route being used for the following
path:
|
The operations listed in the following table might cause a path being used to be disconnected. |
Operations that might cause a disconnection
| Interface | Window and command |
|---|---|
| HDvM - SN | Add External Volumes window |
| Edit External Path Configuration window | |
| CCI | raidcom add external_grp |
| raidcom add path | |
| raidcom discover external_storage | |
| raidcom discover lun |
When the operations listed in the table above are performed on the Hitachi external storage system, change the connection configurations to use a route that is not being used for an external path or a remote path. Alternatively, verify that any problem will not be caused even if the host I/O performances or the remote copy performances for the external volumes are temporarily degraded before the operations.
When the operations listed in the table above are performed on the non-Hitachi external storage system, use a route that is not being used for an I/O path from the non-Hitachi external storage system to the local storage system.
To operate safely
It is best practice to perform the external path operations by using CCI. You can specify the command option -safety_check enable to suppress a processing that might cause a disconnection from the external storage system to the local storage system for the CCI commands listed in the table above.
- If -safety_check enable is specified for the raidcom discover external_storage command, Unknown is displayed for a route that might be disconnected.
- If the Hitachi external storage system is Unknown, the host I/O performances or the remote copy performances for the external volumes that use the route might be temporarily degraded due to the temporary disconnection. Change the connection configurations to use a route that is not being used for an external path or a remote path. If the temporary performance degradation will not cause any problem, run the command without specifying -safety_check enable.
- If the non-Hitachi external storage system is Unknown, change the connection configurations to use a route that is not being used for the I/O path from the non-Hitachi external storage system to the local storage system.
- For more information, see the Command Control Interface Command Reference.