good explanation of physical volumes

[sanman_2]

Hello everyone,

Can anyone please tell me where can I go to get either a picture or a good understanding or what a logical volume is, physical volume, volume group, etc. Like is there a diagram of some sort that I can look at to get a better understanding of it.

[Kofi ARTHIABAH]

Sanman:

check the hp docs site for the HP-UX System Administration Tasks - Chapter 3 has diagrams explaining LVs and PV etc.

http://docs.hp.com/hpux/pdf/B2355-90672.pdf

Good luck.

[Rainer_1]

this may be a good start
http://www.docs.hp.com/hpux/onlinedocs/B2355-90672/00/00/28-con.html

[Rita C Workman]

Just so you have more than one url, here's another place that will help you and has diagrams....

http://docs.hp.com:80/dynaweb/hpux10/hpuxen0a/b2043/@ebt-link?window=CURRENT;target=%25N%14_4675_START_RESTART_N%25;DwebQuery=lvm

[Patrick Wallek]

Think of it this way:

Physical Volume - A actual physical device. A hard drive in a cabinet. (Could also be a LUN on an array).

Volume Group - A group of physical volumes combined to form a larger area of disk space. (ie. 4 physical volumes(9GB each) /dev/dsk/c1t1d0, c1t2d0,c1t3d0,c1t4d0 combined to form volume group 1 - vg01 with available space of 36 GB).

Logical Volume - An area that is carved out of the volume group allowing data to be stored on it. (ie. logical volume 1 - lvol1 - is created to be 15 GB in size and mounted as /mydata on the system.)

You now have a /mydata directory that has 15 GB available. This 15 GB came from 4 PHYSICAL VOLUMES (c1t1d0, c1t2d0, c1t3d0, c1t4d0) which were combined into a VOLUME GROUP (vg01) on which the LOGICAL VOLUME lvol1 was created. lvol1 was then mounted as /mydata.

I hope this makes more sense to you now.

[Bill McNAMARA_1]

PREPARE:
a Physical Volume is an entire Disk dedicated
for lvm's usage.
ie:pvcreate

COLLECT:
The Volume Group is a collection of Disks
ie: vgcreate, vgextend

USE:
A logical Volume is to use the disk
ie: lvcreate

USE FOR SOMETHING INTERESTING:
Create a filesystem.
newfs

Think of lvm as a layer sitting in between
your filesystem and your disk drivers.
It effectively creates a device file to
create your filesystem on and links that
down to the disk.

[thinphony]

You can use ioscan to display disks attached to the system and their device file names.then use pvcreate command to initialize the disk. After a disk is initialized ,it's called a physical volume. PVs are configured together as volume groups, each PV was devided into many Physical Extents, PEs are maped into Logical Extents, and Logical Volume is made up by LEs. And on LV will be a filesystem or swap area or raw data.
hope this will help .
regards.