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work, host I/O must be pointed at the LVM Logical Volume device, not at the raw or block
special files in /dev/rdsk and /dev/dsk.
WARNING!
as a different device (e.g., cxt0d0 and cyt0d0), the potential to overwrite data on a LUN
exists if I/O is performed directly to the /dev/dsk/ or /dev/rdsk/ special files. The PVLinks
feature is part of LVM volume management. Refer to HP LVM documentation (available at
http://docs.hp.com) for information on using PVLinks. One such reference is the following HP
document: Managing Systems and Workgroups: A Guide for HP-UX System Administrators,
HP 9000 Computers Edition 5, Manufacturing Part Number: B2355-90742, Chapter 6,
"Administering a System: Managing Disks and Files," Section, "Setting Up Alternate Links to
a Physical Volume."
Alternate links (paths) to a volume are defined at the volume group level using the vgcreate
command or by using the SAM GUI.
# sam > Disk and File systems > Volume Groups & Logical Volumes
The order of failover paths specified during volume creation is important, as the failover priority
will be considered in the same order as used when the volume was created. For example:
# vgcreate <volume name> <path1> <path2> <path3>...<pathn>
The failover path for the primary active path will be increased by 1 up to path n.
NOTE:
alternate links by default.
After the primary link has recovered, LVM will automatically switch the active I/O from the
alternate path to the primary path unless you previously instructed it not to by using the
pvchange LVM command.
After initial volume-group setup, path management is manipulated at the physical-volume level
using HP-UX pv... commands. To display the paths to a device, and the status of each path,
use HP-UX's pvdisplay /dev/dsk/... command. To display the paths to all devices
within a volume-group, use HP-UX's vgdisplay -v command. The following example shows
partial output from these commands:
# vgdisplay -v
--- Logical volumes ---
LV Name
LV Status
LV Size (Mbytes)
Current LE
Allocated PE
Used PV
--- Physical volumes ---
PV Name
PV Name
PV Status
Total PE
Free PE
Autoswitch
38
Allocating Storage for Access by the HP-UX Host
Because HP-UX sees every path to a device (i.e., a single storage server VLUN)
If you are using the SAM utility to create volume groups, it creates all possible
/dev/testdg/testvol1
available/syncd
10000
2500
2500
1
/dev/dsk/c120d1
/dev/dsk/c14t0d1 Alternate Link
available
2559
0
On
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