130Administering dynamic multipathing (DMP)

How DMP works

DMP coexistence with HP-UX native multipathing

The HP-UX 11i v3 release includes support for native multipathing, which can coexist with DMP. HP-UX native multipathing creates a persistent (agile) device in the /dev/disk and /dev/rdisk directories for each disk that can be accessed by one or more physical paths. To maintain backward compatibility, HP-UX also creates legacy devices in the /dev/dsk and /dev/rdsk directories.

VxVM recreates disk devices for all paths in the operating system’s hardware device tree as DMP nodes in the /dev/vx/dmp and /dev/vx/rdmp directories, independently of the devices that are listed in the /dev/dsk and /dev/rdsk directories. VxVM uses a DMP node to represent a disk that can be accessed by one or more physical paths. DMP nodes are not used by the native multipathing feature of HP-UX.

VxVM commands display device names according the naming scheme that has been selected.

See “Changing the disk-naming scheme” on page 91.

By default, VxVM is configured to use DMP metanodes. If you want to use HP-UX native multipathing, you must add the HP-UX native multipathing metanodes as foreign devices.

See “Adding foreign devices” on page 89.

See “Migrating between DMP and HP-UX native multipathing” on page 130.

For instructions on administering native multipathing with Base-VxVMand VxVM-Full, please consult the Release Notes for VxVM 5.0 on 11i v3.

Migrating between DMP and HP-UX native multipathing

You can use the vxddladm addforeign and vxddladm rmforeign commands to migrate a system between using DMP and using HP-UX native multipathing. These procedures migrate all devices in the /dev/disk and /dev/rdisk directories.

Caution: Before migrating between DMP and HP-UX native multipathing, ensure that no applications are accessing VxVM volumes. Migration is not supported without first stopping any applications that are using the volumes.

To migrate from DMP to HP-UX native multipathing1Stop all the volumes in each disk group on the system:#vxvol -g diskgroup stopall2Use the following commands to initiate the migration:#vxddladm addforeign blockdir=/dev/disk chardir=/dev/rdisk#vxconfigd -kr reset