Improves the availability, disk I/O, performance and capabilities of disk management
Adds an extra layer between the physical disks and the file system, allowing you to create a logical volume instead of a physical disk
Allows you to easily resize, extend and decrease the LV when need it
How to Create LVM Physical Volumes:
# ls /sys/class/scsi_host
host0
# echo "- - -" > /sys/class/scsi_host/host0/scan
Check disk:
fdisk -l
General syntax for the creation of Phisical Volume (pvcreate)
pvcreate <Physical Volume name>
# pvcreate /dev/sdb /dev/sdc /dev/sdd
Physical volume "/dev/sdb" successfully created
Physical volume "/dev/sdc" successfully created
Physical volume "/dev/sdd" successfully created
Use the pvdisplay and pvs commands to display the PVs you have created. The pvs command shows summarize output and the pvdisplay shows the detailed output of the PVs.
# pvdisplay
"/dev/sdb" is a new physical volume of "15.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb
VG Name
PV Size 15.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID 69d9dd18-36be-4631-9ebb-78f05fe3217f
"/dev/sdc" is a new physical volume of "15.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdc
VG Name
PV Size 15.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID a2092b92-af29-4760-8e68-7a201922573b
"/dev/sdd" is a new physical volume of "15.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdd
VG Name
PV Size 15.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID d92fa769-e00f-4fd7-b6ed-ecf7224af7faS
How to Create a Volume Group:
General syntax for Volume Group Creating (vgcreate)
vgcreate [Volume Group Name] [Physical Volume Name]
Use the following command to add a new physical volume to the new volume group.
# vgcreate vg01 /dev/sdb /dev/sdc /dev/sdd
Volume group "vg01" successfully created
*Note:* By default, it uses 4MB for physical extent, but you can change it based on your need.
Use the vgs and vgdisplay commands to display information about the VG you created.
vgdisplay vg01
--- Volume group ---
VG Name vg01
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 3
Act PV 3
VG Size 44.99 GiB
PE Size 4.00 MiB
Total PE 11511
Alloc PE / Size 0 / 0
Free PE / Size 11511 / 44.99 GiB
VG UUID d17e3c31-e2c9-4f11-809c-94a549bc43b7
How to Extend Volume Group:
If you do not have space in the VG, Use the following command to add a new physical volume to the existing volume group.
Common syntax for Volume Group extension (vgextend).
vgextend [Existing Volume Group Name] [Physical Volume Name]
vgextend vg01 /dev/sde
Volume group "vg01" successfully extended
How to Create Logical Volume Using GB Size's:
General syntax:
lvcreate –n [Logical Volume Name] –L [Logical Volume Size] [Name of the Volume Group where the LV to be created]
Run the below command to create a logical volume lv001 of size 10 GB.
# lvdisplay /dev/vg01/lv001
--- Logical volume ---
LV Path /dev/vg01/lv001
LV Name lv001
VG Name vg01
LV UUID ca307aa4-0866-49b1-8184-004025789e63
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2020-09-10 11:43:05 -0700
LV Status available
# open 0
LV Size 10.00 GiB
Current LE 2560
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
How to Create Logical Volume Using PE Size’s
Alternatively, you can create Logical Volumes Using Physical Extends (PE) size.
How to Calculate PE Value? It’s very simple, for example, if you have a volume group of 10 GB, then what is the PE size?
By default, it uses 4MB for the physical extent, but check the correct PE size by running the vgdisplay command, as this can be changed based on requirements.
10GB = 10240MB / 4MB (PE Size) = 2560 PEs
Common syntax for Logical Volume Creation with PE Size’s (lvcreate).
lvcreate –n [Logical Volume Name] –l [Physical Extends (PE) Size] [Name of the Volume Group where the LV to be created]
To create 10GB of logical volume using the PE size the command would be:
# lvcreate -n lv001 -l 2560 vg01
How to Create File system
You cannot use a logical volume until you create a valid file system.
General syntax to create a file system.
mkfs –t [File System Type] /dev/[Name of the Volume Group where LV resides]/[LV name]
Use the below command to format the logical volume lv001 with the ext4 file system.
# mkfs -t ext4 /dev/vg01/lv001
For xfs file system.
# mkfs -t xfs /dev/vg01/lv001
Mounting Logical Volume Finally, you need to mount the logical volume to use it. Make sure to add an entry to /etc/fstab so that it loads automatically when the system boots.
Create a directory to mount the logical volume.
# mkdir /lvmtest
Use the mount command to mount the logical volume.
# mount /dev/vg01/lv001 /lvmtest
Add new logical volume details to the /etc/fstab file to mount automatically when the system starts.
# vi /etc/fstab
/dev/vg01/lv001 /lvmtest xfs defaults 0 0
Check the newly mounted volume using the df command.