| Commands | Section 2: LVM Logical Volumes >

1. Introduction

https://www.udemy.com/course/a-complete-guide-on-linux-lvm/learn/lecture/13069906#overview

2. The LVM Manager Overview

Traditional Partitioning

• You cannot resize partitions
• You cannot add disks together to create a single drive

Using LVM

• You can combine multiple drives into a single volume group
• The pool can be subdivided into smaller Logical Volumes (LV)
• Any remaining space can be added to a LV.
• Additional drives can be added to the Pool

3 Features of LVM

• Additional flexibility
• Disks can be added to the pool then subdivided in to Logical Volumes
• LVs can be resized
  • LVs can be moved around (advanced)
• LVM can be though of Dynamic Partitions
  • Create / Resize / Delete “On the fly”

4. LVM Architecture Overview

Terminology

• PV Physical Volume
  • Can be a whole disk or a partition
• Volume Groups
  • 1 or more PVs combined into a group
• LV
  • Partitions of the VG
  • Can be formatted as desired
    • ext4
    • nfs

5. Architecture Diagram

https://www.udemy.com/course/a-complete-guide-on-linux-lvm/learn/lecture/13061948#overview

6. LVM Components

• Physical Volumes PV
  • Block device
  • LVM Label placed in the second 512 byte sector by default
    • First sector = mbr (Master Boot Record)
      • Can be placed in any of the first 4 sectors
    • Label provides information about
      • Identification
      • Device ordering (since any device can come up in any order when a system is booted)
    • Labels remain persistent across reboots
    • Contains random unique UUID for the physical volume.
  • 3rd & 4th sectors contain metadata
    • See next section

7. Practice Lab

• About Metatdata
  • How and when the volume was created
  • Information about the Volume Group
    • Name and Unique ID
    • Version Number
      • Incremented whenever the metadata is updated
      • Read write properties
      • Any admin limits on the number of PV and LVs it may contain.

Creating the Physical Volumes

1. Create the Partition
   1. For a full disk, the first partition starts at 2048 (first 4 512 sectors reserved!)
   2. Use the rest of the disk as Primary p
   3. Type t – 8e (Linux LVM)
   4. Write / Quit
   5. Continue with any remaining disks
2. Create an LVM physical volume
   1. pvcreate /dev/sdb1
   2. Repeat for any remaining disks
3. Get data for the individual PVs
   1. pvdisplay /dev/sdb1
      1. PV Name
      2. VG Name
      3. PV size
      4. Allocat