One 、 Problems with traditional disk management

When the partition size is not enough, its size cannot be expanded , Only by adding disks 、 Create new partitions to expand space , But the newly added hard disk exists as a separate file system , The original file system has not been expanded , The upper application can only access one file system many times . Only existing disks can be taken offline , After replacing with a new disk , Then import the original data into .

Two 、LVM The basic concept of logical volume

LVM（Logical volume Manager） Logical volume management encapsulates the underlying physical hard disk abstractly , In the form of logical volume, it is presented to the upper system , The size of the logical volume can be adjusted dynamically , And there's no loss of existing data . The newly added hard disk will not change the existing upper level logical volume .

As a dynamic disk management mechanism , Logical volume technology greatly improves the flexibility of disk management .

PE（physical extend） The default is 4MB The basic block of

PV（physical volume） Hard disk or partition

VG（volume group） By one or more PV The whole of composition

LV（logical volume） from VG The space cut out in is used to create a file system

3、 ... and 、LVM The creation process

  1. The physical disk is formatted as PV, Space is divided into one by one PE
  2. It doesn't work PV Join the same VG, Different PV Of PE All in VG Of PE In the pool
  3. LV be based on PE establish , The size is PE Integer multiple , form LV Of PE Probably from different physical disks
  4. LV Now you can directly format it and mount it
  5. LV The expansion and reduction of is actually to increase or decrease the composition of the LV Of PE The number of . The process does not lose the original data

Four 、 establish LVM

Initialize the physical disk device as a physical volume

pvcreate /dev/sdb /dev/sdc

Create a volume group , And will PV Join 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 the formatted logical volume

mount /dev/vg0/lv0 /mnt/

Write the mount information to /etc/fstab Medium restart still works

echo "/dev/vg0/lv0 /mnt ext4 defaults 0 0 " >> /etc/fstab

5、 ... and 、 see LVM

View physical volume information ：pvs、pvdisplay（ detailed ）

View volume group information ：vgs、vgdisplay（ detailed ）

View logical volume information ：lvs、lvdisplay（ detailed ）

6、 ... and 、 Delete LVM

Delete LV：lvremove /dev/vg0/lv0

Delete VG：vgremove vg0

Delete PV：pvremove /dev/sdb

7、 ... and 、 Stretch a logical volume

The stretch operation of the logical volume can be performed online , No need to unmount logical volumes

Guarantee VG There is enough free space in

vgs、vgdisplay

Expand logical volume

lvextend -L +5G /dev/vg0/lv0

After viewing the expansion LV size

lvs、lvdisplay

Update the file system

resize2fs /dev/vg0/lv0

View the updated file system

df –h

8、 ... and 、 Stretch a roll group

Will be added to VG The hard disk of is formatted as PV

pvcreate /dev/sdd

New PV Add to specified volume group

vgextend vg0 /dev/sdd

After viewing the expansion VG size

vgs、vgdisplay

Nine 、 Shrink a logical volume

The shrink operation of the logical volume must be performed offline , To unmount a logical volume

Unmount logical volumes that have already been mounted

umount /dev/vg0/lv0

Shrink the file system （ primary lv0 by 10G）

e2fsck -f /dev/vg0/lv0

resize2fs /dev/vg0/lv0 3G

narrow LV

lvreduce -L -7G /dev/vg0/lv0

Look at the reduced LV

lvs、lvdisplay

mount

mount /dev/vg0/lv0 /mnt

Ten 、 Reduce the volume group

Will a PV Remove... From the specified group

vgreduce vg0 /dev/sdd

View the reduced volume group size

vgs、vgdisplay

remove PV

pvremove /dev/sdd

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