Basic concepts and Management of LVM
I. Problems with traditional disk management
When the partition size is insufficient, it cannot be expanded. You can only add a disk or create a new partition to expand the space. However, the newly added hard disk exists as an independent file system, the original file system is not extended, and upper-layer applications can only access one file system. You can only deprecate an existing disk, replace it with a new disk, and then import the original data.
Ii. Basic concepts of LVM logical volumes
The Logical volume Management of LVM (Logical volume Manager) abstracts the underlying physical hard disks and presents them to the upper-layer system as Logical volumes. The Logical volume size can be dynamically adjusted, and existing data will not be lost. The new hard disk does not change the logical volume on the upper layer.
As a dynamic disk management mechanism, logical volume technology greatly improves the flexibility of disk management.
PE (physical extend) is a basic block of 4 MB by default.
PV (physical volume) hard disk or partition
VG (volume group) is composed of one or more PVS.
The space cut by LV (logical volume) from VG is used to create a file system.
Iii. LVM creation process
1. The physical disk is formatted as PV, and the space is divided into PES.
2. Add the same VG to PV without passing through. All pes with different PVS enter the PE pool of VG.
3. LV is created based on PE and the size is an integer multiple of PE. The PE that makes up LV may come from different physical disks.
4. LV can be directly formatted and mounted and used now.
5. LV expansion and reduction is actually to increase or decrease the number of PES that make up the LV. The process does not lose raw data.
4. Create LVM
Initialize a physical disk device as a physical volume
Pvcreate/dev/sdb/dev/sdc
Create a volume group and add PV to the volume group
Vgcreate vg0/dev/sdb/dev/sdc
Create logical volumes based on volume groups
Lvcreate-n lv0-L 5G vg0
Create a file system for the created logical volume
Mkfs. ext4/dev/vg0/lv0
Mount and use formatted logical volumes
Mount/dev/vg0/lv0/mnt/
The mounting information is written to/etc/fstab and restarted.
Echo "/dev/vg0/lv0/mnt ext4 defaults 0 0">/etc/fstab
5. View LVM
View physical volume information: pvs and pvdisplay (details)
View volume group information: vgs and vgdisplay (details)
View logical volume information: lvs and lvdisplay (details)
6. Delete LVM
Delete LV: lvremove/dev/vg0/lv0
Delete VG: vgremove vg0
Delete PV: pvremove/dev/sdb
7. Stretch a logical volume
The logical volume stretching operation can be performed online without detaching the logical volume.
Ensure sufficient free space in VG
Vgs, vgdisplay
Expand logical volume
Lvextend-L + 5G/dev/vg0/lv0
View the expanded LV size
Lvs and lvdisplay
Update File System
Resize2fs/dev/vg0/lv0
View the updated File System
Df-h
8. Stretch a volume group
Format the hard disk to be added to VG as PV
Pvcreate/dev/sdd
Add a new PV to a specified volume group
Vgextend vg0/dev/sdd
View the expanded VG size
Vgs, vgdisplay
9. Narrow down a logical volume
The logical volume downgrading operation must be performed offline. You must detach the logical volume.
Detach a mounted logical volume
Umount/dev/vg0/lv0
Shrink the file system (the original lv0 is 10 Gb)
E2fsck-f/dev/vg0/lv0
Resize2fs/dev/vg0/lv0 3G
LV reduction
Lvreduce-L-7G/dev/vg0/lv0
View the resized LV
Lvs and lvdisplay
Mount
Mount/dev/vg0/lv0/mnt
10. shrink the volume group
Removes a PV from a specified group.
Vgreduce vg0/dev/sdd
View the size of the reduced volume group
Vgs, vgdisplay
Remove PV
Pvremove/dev/sdd
LVM2 details
Use LVM on Ubuntu to easily adjust partitions and create snapshots
Use LVM to create elastic disk storage-Part 1
Expanding/downgrading LVM in Linux (Part 2)
Recording and restoring logical volume snapshots in LVM (part 3)
Set a streamlined resource allocation volume in LVM (part 4)
Use fragmented I/O to manage multiple LVM disks (Part 5)
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