New Changes in HPUX 11iv3 LVM

From HP-UX 11i V3, disk devices can be represented by two different types of device files in the/dev directory: Old device files and persistent device files.

The old device file is the only type of the NAS file for HP-UX 11i V3 and earlier versions. Such files include hardware path information such as SCSI bus, destination and encoded Lun in the device file name and number. For example, the old Device File/dev/DSK/c3t2d0 indicates that the disk is located on the card instance 3, the target address 2, and the Lun address 0.

The persistent device file is independent of the physical hardware path to the disk. It maps to the unique GLobal IDEntifier (wwid) of the disk (similar to PVID in Aix ).

 

Therefore, if the disk is moved from one interface to another, from one switch/hub port to another, or is provided to the host through different target ports, the device file remains unchanged. Persistent device file names follow a simple

Naming Convention:/dev/Disk/diskn. N indicates the instance number assigned to the disk. The device file name and serial number do not contain any hardware path information.
In addition, if the disk has multiple hardware paths, it is represented by a persistent device file. Persistent Device Files process multi-path disks transparently, replacing the LVM multi-path feature described in "Improve availability through multi-path. If the disk has multiple hardware paths (LVM is called pvlink), dedicated persistent device files are used as a single access point for all links. Massive storage stacks are selected using the load balancing algorithm to allocate I/O requests to all available links. If a link fails, the massive storage stack will automatically disable the faulty link and continue to perform I/O operations on all other links. All faulty or unresponsive links are monitored so that when a faulty link returns to normal, it is automatically and transparently added to the load balancing. You can also automatically discover new magnetic disks and links and add them to Server Load balancer.

If there is any change in disk connectivity (such as link addition, deletion, or modification), as long as at least one link is active, the programs that use persistent device files will not be affected. A new disk is automatically found.

For LVM disks, you can use persistent device files or old device files. We recommend that you use dedicated persistent device files for LVM disks to support more load balancing options.

Note:If you want to use the LVM backup link feature, you must use old device files and disable the multi-path feature through these old device files.
It should be said that this is similar to IBM's AIX volume management function and is more practical. Hpux lvm has always followed the original idea. This time it should be a big adjustment.