Friday, February 20, 2009

Placing disks under VxVM control

When you add a disk to a system that is running VxVM, you need to put the disk under VxVM control so that VxVM can control the space allocation on the disk.

you can change the naming scheme from the command line. The
following commands select enclosure-based and operating system-based
naming respectively:

# vxddladm set namingscheme=ebn [persistence={yes|no}]

# vxddladm set namingscheme=osn [persistence={yes|no}]

The change is immediate whichever method you use. The optional persistence
argument allows you to select whether the names of disk devices that are
displayed by VxVM remain unchanged after disk hardware has been
reconfigured and the system rebooted. By default, both enclosure-based naming
and operating system-based naming are persistent.

To find the relationship between a disk and its paths, run one of the following

# vxdmpadm getsubpaths dmpnodename=disk_access_name

# vxdisk list disk_access_name

To update the disk names so that they correspond to the new path names
1 Remove the file that contains the existing persistent device name database:

# rm /etc/vx/

2 Restart the VxVM configuration demon:

# vxconfigd -k

This regenerates the persistent name database.

Discovering the association between enclosure-based disk names
and OS-based disk names
If you enable enclosure-based naming, and use the vxprint command to display
the structure of a volume, it shows enclosure-based disk device names (disk
access names) rather than c#t#d#s# names. To discover the c#t#d#s# names
that are associated with a given enclosure-based disk name, use either of the
following commands:

# vxdisk -e list enclosure-based_name

# vxdmpadm getsubpaths dmpnodename=enclosure-based_name

For example, to find the physical device that is associated with disk ENC0_21,
the appropriate commands would be:

# vxdisk -e list ENC0_21

# vxdmpadm getsubpaths dmpnodename=ENC0_21

To obtain the full pathname for the block and character disk device from these
commands, append the displayed device name to /dev/vx/dmp or /dev/vx/rdmp

Simple or nopriv disks in the boot disk group
If the boot disk group (usually aliased as bootdg) is comprised of only simple and/or nopriv disks, the vxconfigd daemon goes into the disabled state after the naming scheme change.
To remove the error state for simple or nopriv disks in the boot disk group
1 Use vxdiskadm to change back to c#t#d#s# naming.
2 Enter the following command to restart the VxVM configuration daemon:

# vxconfigd -kr reset

3 If you want to use enclosure-based naming, use vxdiskadm to add a sliced disk to the bootdg disk group, change back to the enclosure-based naming scheme, and then run the following command:

# /etc/vx/bin/vxdarestore

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