Establish paths to I/O groups on hosts

After the system adds the new I/O group to the volume's access set and you move selected volumes to a new I/O group, you must detect the new paths to the volumes on the host. The commands and actions on the host varies depending on the type of host and the connection method that is used by the hosts. These steps must be completed on all hosts to which the selected volumes are currently mapped.

The management GUI lists all the host mapping details that are necessary when you move volumes to a new I/O group. The host mapping details show volumes and their associated unique identifiers (UIDs) that identify the volume on each host. You can use these details to verify that the hosts detected the paths to the new I/O group.

Since the system supports many different types of hosts, these steps use a Linux (RHEL 6.1 or SLES 11 SP1) host as an example throughout these instructions.

Note: The instructions assume that all volumes are mapped to Fibre Channel hosts. For instructions on moving volumes that are mapped to iSCSI hosts, see Moving volumes mapped to iSCSI hosts to another I/O group

For instructions about detecting paths to volumes on other types of hosts, see the corresponding documentation that came with your host.

The system supports many different host systems and host bus adapters (HBAs). The following website provides current interoperability information. This information includes current support information, such as maximum configuration details, technical flashes, hints, and tips, host systems, operating system levels, HBAs, cables, and fabrics that are supported.

To establish paths to the new I/O group on the host system, complete these steps:

Log on to the Linux host and for each Fibre Channel host port, run the command:
```
echo "- - -" > /sys/class/scsi_host/hostx/scan
```
Ensure that the Device Mapper Multipath (DMMP) detects the new paths by entering the following command:
```
multipath -v2
```
To verify that the paths that are related to the new I/O group are ready, submit the following command:
```
multipath -ll
```
The paths to the new I/O group display a status of Active Ready.
Verify that the host is able to use the new paths. If DMMP enables the preferred paths, ensure that the preferred paths correspond to the selected preferred node.