What is LVM (Logical Volume Management)?

LVM is a tool for logical volume management which includes appropriate disks, striping, mirroring and realizing logical volumes.

With LVM, a hard drive or set of hard drives is allocated to one or other physical volumes. LVM physical volumes can be arranged on other block devices which efficiency span two or more disks. The physical volumes are mixed into logical volumes, with the exclusions of the /boot/ partition. The /boot/ partition cannot be on a logical volume group because the boot loader cannot read it. If the root (/) partition is on a logical volume, create a separate /boot/ partition which is not a part of a volume group. Logical Volume management is an important topic in the Linux that you can practically with Linux Training in Chandigarh.

LVM is used for the following purposes:

Managing extensive hard disk area by grant disks to be added and replaced without downtime or service delay, in merger with hot substitute.
Creating single sensible quantity of various essential amount or complete hard disks , allowing for destructive volume resizing.
On small systems rather having to completions at accessions time how large a partition might need to be, LVM gives acceptance filesystems to be simply resized as required.
Performing logical backups by taking snapshots of the logical volumes.
Encrypting various environmental barriers with one password.

LVM can be manage as a delicious software layer on dominated of the hard disks and boundary, which creates an reflections of dependability and ease of use for charge hard drive restoration and backup.

Basic functionality of LVM

Volume groups can be consist by arresting new physical volumes (PVs) online and bump original ones.
Logical volumes can be resides online by join amount onto them or compress extents.
LVs can be moved between PVs.
establishment of read-only snapshots of logical volumes and read-write snapshots .
Volume Groups can be selection or absorb in site as long as no LVs age the division. This can be useful when depart whole obvious Volume to or from disconnected deport.
LVM objects can be tagged for administrative advantage.
VGs and LVs can be built active as the invisible devices become present through use.
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Advanced functionality of LVM

Hybrid volumes can be build using the dm-cache target, which grant one or more fast deport devices, such as burst-based SSDs, to actions as a wealth for one or more heavy hard disk drives.
Easily coddle LVs can be apportion from a pool.
On advanced versions of device surveyor, LVM is unified with the vacations of device mapper suitable to ignore the particular directions that back a dm-multiple device if devices multipath_component_detection=1 is set in lvm.conf. This prohibits LVM from stimulate volumes on an individual path rather of the multiple device.

LVM Structure

The structure of a Logical Volume Manager disk humidity is adored given below. Logical Volume Management empower the connecting of different original hard drives and/or disk barriers into a single volume group (VG). That volume body can then be partitions into relevant volumes (LV) or used as a original large volume. Regular file systems, such as EXT3 or EXT4, can then be build on a logical volume.

The two entire physical hard drives and one division from a third hard drive have been connected into a single volume part. Two logical volumes have been completed from the capacity in the volume associate, and a filesystem, such as an EXT3 or EXT4 filesystem has been prompt on each of the two flexibility volumes.

Adding disk space to a host is moderately straightforward but, in my experience, is done almost occasionally. The basic steps needed are recorded below. You can each of two create an absolutely new volume group or you can add the new space to an actual volume group and either develop an existing logical volume or create a new one.

Adding a new Logical Volume Management

There are times when it is basic to add a new logical volume to a host. For example, after observing that the directory consist virtual disks for my Virtual Box virtual machines was dressing up the /home file system, I decided to create a new obvious volume in which to store the virtual machine data, including the virtual disks. This would free up a great deal of space in my /home value system and also allow me to regulate the disk space for the VM\’s independently. The basic steps for adding a new logical volume are as follows.

If necessary, install a new hard drive.
Optional: Create a barrier on the hard drive.
Create a physical volume (PV) of the exhaustive hard drive or a partition on the hard drive.
Assign the new physical volume to an current volume group (VG) or create a new volume group.
Create a new logical volumes (LV) from the capacity in the volume group.
Create a filesystem on the new logical volume.
Add relevant entries to etc fstab for mounting the filesystem.
Mount the file system.

Resizing a logical volume in an LVM file system

The need to resize a filesystem has been about since the starting of the first versions of Unix and has not gone away with Linux. It has earned simply, however, with Logical Volume Management.

If necessary, install a new hard drive.
Optional: Create a partition on the hard drive.
Create a physical volume (PV) of the entries hard drive or a partition on the hard drive.
Assign the new physical volume to an actual volume group (VG) or create a new volume group.
Create one or more relevant volumes (LV) from the space in the volume group, or expand an actual logical volume with some or all of the new space in the volume group.
If you build a new logical volume, create a filesystem on it. If adding space to an current logical volume, use the resize command to augment the filesystem to fill the space in the sensible volume.
Add relevant entries to /etc/fstab for arise the filesystem.
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