Series of the tutorial to learn LVM commands. In this part of the tutorial, learn how to create physical volume and how to view its details (pvcreate, pvdisplay)
We are starting this tutorial series for LVM (Logical Volume Manager) which is a widely used volume manager in HPUX and some Linux flavors too. This tutorial will be split into 4 parts :
- Part 1: Physical Volume (pvcreate, pvdisplay)
- Part 1: Physical Volume (pvchange, pvmove)
- Part 2: Volume group (vgcreate, vgdisplay, vgscan)
- Part 2: Volume group (vgextend, vgreduce, vgexport, vgimport)
- Part 2 : Volume group (vgcfgbackup, vgcfgrestore, vgchange)
- Part 2: Volume group (vgremove, vgsync)
- Part 3: Logical Volume (lvcreate, lvdisplay, lvremove)
- Part 3: Logical Volume (lvextend, lvreduce, lvchange)
- Part 3: Logical Volume (lvsync, lvlnboot)
Let’s dive into the first part i.e. physical volume.
A physical volume is a raw disk presented to the operating system. It can be a local disk, LUN from remote storage, disk from local disk array, etc. All storage disks from these types are formatted as physical volumes under LVM so that those can be used in definite file systems.
Lets start with the first command to create physical volume. Before using this command you need to confirm your new raw disk on OS. You can use
ioscan -fnCdisk command or confirm by checking into
Note : /dev/rdsk/cXdXtX is legacy naming conventions (HPUX 1111,11.21,10.x) whereas /dec/rdisk/diskX is persistent naming convention (11.21, 11.31).
Now that you identified new disk presented to server lets say
/dev/rdisk/disk3 for example, you can run
pvcreate command to create physical volume out of it.
# /usr/sbin/pvcreate /dev/rdisk/disk3 Physical volume "/dev/rdisk/disk3" has been successfully created.
The command outputs success message confirming PV has been created. Note here that you should use character device file i.e. with
If by mistake you put in wrong disk name or disk is already being used in LVM on the same server then the command will fail. If you presented disk which was used earlier on another server and now you want to use it here with data loss then
-f option can be used to forcefully create PV by destroying any data present on the disk. Note here that
-f option do not ask any confirmation before deleting data.
There are other options can be used with this command which are:
-Bto make it bootable disk. Used during root disk mirroring
-b, -drelated to bad blocks
-sto specify effective size. Normally everyone uses full disk so this options doesn’t matter much
Normally these options are not used when we are aiming at PV for mount point usage only. Hence we are not going drill down these options.
Now, PV has been created one can see its details with
# /usr/sbin/pvdisplay /dev/disk/disk3 --- Physical volumes --- PV Name /dev/disk/disk3 VG Name PV Status available Allocatable yes VGDA 2 Cur LV 0 PE Size (Mbytes) 32 Total PE 1557 Free PE 1557 Allocated PE 0 Stale PE 0 IO Timeout (Seconds) default Autoswitch On Proactive Polling On
Here many fields are self-explanatory. Refer LVM legends to have a better understanding. From this output, you can also calculate disk size. Total PE x PE size = Disk size (available to use i.e. after formatting space loss)
If you want to drill down PE details i.e. which PE is serving which LV then
-v option can be used. This is helpful when the disk has bad sectors. Below is the output in which PV is part of the volume group already.
# /usr/sbin/pvdisplay -v /dev/disk/disk3 --- Physical volumes --- PV Name /dev/disk/disk3 VG Name /dev/vg01 PV Status available Allocatable yes VGDA 2 Cur LV 1 PE Size (Mbytes) 32 Total PE 1557 Free PE 0 Allocated PE 1557 Stale PE 0 IO Timeout (Seconds) default Autoswitch On Proactive Polling On --- Distribution of physical volume --- LV Name LE of LV PE for LV /dev/vg01/lvol1 1557 1557 --- Physical extents --- PE Status LV LE 00000 current /dev/vg01/lvol1 00000 00001 current /dev/vg01/lvol1 00001 00002 current /dev/vg01/lvol1 00002 00003 current /dev/vg01/lvol1 00003 00004 current /dev/vg01/lvol1 00004 00005 current /dev/vg01/lvol1 00005 00006 current /dev/vg01/lvol1 00006 00007 current /dev/vg01/lvol1 00007 00008 current /dev/vg01/lvol1 00008 00009 current /dev/vg01/lvol1 00009 00010 current /dev/vg01/lvol1 00010 00011 current /dev/vg01/lvol1 00011 00012 current /dev/vg01/lvol1 00012 ----- output truncated -----
Here you can see how PV is distributed among different LV. and furthermore, it gives you table mapping of PE to LE! There are numerous options can be used with this command but normally -v is used commonly.
There are two more commands used for PV operations:
pvmove. We covered theme commands in the next post.
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