Introduction to lvm software under Linux - elastically scaling the size of the file system

We often encounter such a situation. As the system runs, it is found that the remaining space of a certain partition is insufficient, so the partition needs to be expanded. How to expand the capacity? A common strategy is to

• add a new hard drive, then partition and format it to create a new usable partition.

• Copy the previous file system contents to other partitions, and then unmount the original partition (if the original file system is mounted in the /www directory)

• Mount the new partition to the original directory /www, and then copy the previous content to the /www directory.

Doesn’t the whole process seem quite troublesome? If the original file system space is particularly large, tens of gigabytes or even hundreds of gigabytes, then it will be a huge amount of work. In addition, the previous partition has no use now, which is also a waste!

lvm introduction

lvm logical volume is used to solve the above problems. It can easily expand the size of the file system. For lvm, there are several special nouns you need to know:

• Physical Volume, referred to as PV: physical volume

• Volume Group, referred to as VG: logical Volume group

• ##Logical Volume, referred to as LV: Logical volume

• Physical Extent, referred to as PE: (physical volume) The minimum storage that can be allocated The unit is called a PE, and the size of the PE can be specified.

For the relationship between PV, VG, and LV, you can understand it through the following figure

##lvm usage process Let’s look at the lvm usage process, which is mainly divided into the following stages:

Disk partition
Use partition to create pv
Create vg with pv
Split lv from vg
Format lv and mount it in the directory using
Disk partitioning This step is the same as before, use the fdisk or gdisk tool to partition. The next step is the process of creating a pv. This step is also simple. There is a special tool pvcreate to create it. Like the pv process, the vg stage and lv stage also have specialized vgcreate and lvcreate tools. Elastic expansion and contraction of the size of the file system is achieved by adjusting the size of the lv.

In fact, the use of lvm is very simple. It mainly depends on understanding the above proper nouns. After understanding, you can apply it flexibly. Next, we will prepare several articles to introduce some commands of lvm, as well as practical demonstrations.

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