The Logical Volume Manager (LVM) is a tool that allows the creation and management of logical volumes on Linux systems. Logical volumes are partitions that can span multiple physical disks and can be resized or deleted without affecting the rest of the system. Some of the benefits of using LVM are:

To dynamically change the size of logical volumes. LVM allows the user to increase or decrease the size of a logical volume without having to repartition the disk or reboot the system. This can be useful for allocating more space to a volume that is running out of space, or freeing up space from a volume that is not needed anymore.

To create snapshots. LVM allows the user to create a snapshot of a logical volume, which is a copy of the volume at a certain point in time. Snapshots can be used for backup purposes, as they can be restored to the original volume if needed. Snapshots can also be used for testing purposes, as they can be mounted as read-only or read-write volumes without affecting the original volume.

To dynamically create or delete logical volumes. LVM allows the user to create or delete logical volumes on the fly, without having to repartition the disk or reboot the system. This can be useful for creating temporary volumes for specific purposes, or deleting volumes that are no longer needed.

LVM cannot be used for the following purposes:

To create RAID 9 arrays. RAID 9 is not a valid RAID level, and LVM does not support RAID functionality. RAID is a technique that uses multiple disks to provide redundancy, performance, or both. RAID can be implemented at the hardware level, by using a RAID controller, or at the software level, by using tools such as mdadm or dmraid. LVM can work on top of RAID devices, but it cannot create them.

To encrypt logical volumes. LVM does not provide encryption functionality. Encryption is a technique that protects data from unauthorized access by using a secret key to transform the data into an unreadable form. Encryption can be implemented at the disk level, by using tools such as dm-crypt or LUKS, or at the file system level, by using tools such as eCryptfs or EncFS. LVM can work on top of encrypted devices, but it cannot encrypt them.

References:

LPI Linux Essentials - Topic 3: Command Line Operations

LPI Linux Essentials - Topic 4: User Interfaces and Desktops

LPI Linux Essentials - Topic 5: Administrative Tasks

LPI Linux Essentials - Topic 6: Essential System Services

LPI Linux Essentials - Topic 7: Networking Fundamentals

LPI Linux Essentials - Topic 8: Security Fundamentals

LPI Linux Essentials - Topic 9: Basic Scripting

LPI Linux Essentials - Topic 10: IT Explorations

LPI Linux Essentials - Topic 11: Finding Your Way on a Linux System

LPI Linux Essentials - Topic 12: The Power of the Command Line

LPI Linux Essentials - Topic 13: The Linux Operating System

LPI Linux Essentials - Topic 14: Security and File Permissions

LPI Linux Essentials - Topic 15: Basic Linux System Administration

LPI Linux Essentials - Topic 16: Quotas

LPI Linux Essentials - Topic 17: Managing Users and Groups

LPI Linux Essentials - Topic 18: Ownership and Permissions

LPI Linux Essentials - Topic 19: Special Permissions and Attributes