The LVM of Linux

One: Introduction to LVM

LVM is logicalvolume Manager ( Logical Volume Management ). LVM is the organization of one or more underlying block devices into a logical

Tool that can dynamically add limitations when hard disk space is insufficient or redundant, with great flexibility.

It is to divide the underlying physical volume into multiple PE, which is again divided into logical volumes

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Physical Volume: This refers to the storage device: hard disk, such as:/DEV/SDA,/dev/sdb and other underlying units.

PE: The physical volume is divided into a unit of PE, the size is configurable, the default is 4MB

Volume Group: is a logical physical disk that can consist of multiple physical hard disks that can be created on top of a partition.

logical volumes: similar to partitions on a physical hard disk, created on a volume group.

Two: Create LVM Partitioning

1, create an LVM partition the same way you would create a generic partition, but be aware that the LVM partition number is 8e.

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To see if the creation was successful

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2, create PV

Before you create PV tools to create PV

Pvcreate: Creating PV

PVS: view PV equivalent to pvdisplay

Pvremove: Remove

Pvmove: Mobile

Pvscan: What PV is scanned

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3, create VG

Vgcreate: Create VG

-S specifies the PE size

VGS: view VG equivalent to vgdisplay

Vgremove: Remove VG

Vgmove: Moving VG

Vgextend: Extended VG

Vgreduce: Reduced VG

Vgscan: scanning an existing VG

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3, creating the LV

Lvcreate: creating the LV

-nlv_name: Logical Volume name

-l#unit {MMGGTT}: specifying the logical volume size

Vg_name Volume Group name

LVS: view LV equivalent to lvdisplay

Lvremove: Remove LV

Lvmove: Moving LV

Lvextend: extended LV

Lvreduce: reducing LV

Lvscan: View LV

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access Path to Lv:

1,/etc/vg_name/lv_name

/etc/myvg/mylv

2,/etc/mapper/vg_name-lv_name

/etc/mapper/myvg-mylv

path 1 and Path 2 are symbolic links, pointing to the file /dev/dm-#

Three: extending logical volumes

Create a file system for the logical volume to be created before extending the logical volume and mount it in a free directory

steps to extend a logical volume

1, First determine the size of the expansion target, and ensure that the corresponding volume group has sufficient space available

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2, extend the physical boundary first

Lvextend–l [+] size has a plus sign for how much to extend, no to how much

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at this point, only physical boundaries have been extended, and logical boundaries have not been extended .

3, extending logical Boundaries

RESIZE2FS [ can specify the size of the extension, do not specify the extension to maximum ]/dev/vg_name/lv_name

RESIZE2FS/DEV/MYVG/MYLV: logical size expands to maximum bounds

The result is:

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Four: Reducing logical volumes

Note: The logical volume reduction is offline and the reduced space is able to accommodate the existing data

1, the first step umount unmount The mounted logical volume

2, determine the reduction target size, and ensure that the corresponding logical volume size space is sufficient

3, e2fsck–f Mandatory detection /DEV/MYVG/MYLV

4, First reduce the logical boundary

RESIZE2FS DEVICE size (reduced to how large)

5, reducing physical boundaries

Lvreduce–l [+] size /dev/myvg/mylv

reduction is dangerous, and operation takes care

V: Create a Snapshot volume

Lvcreate

-lsize: Specify Snapshot size

-n:name The name of the snapshot volume

-S: description is snapshot volume

-P: Specifies the access rights of the snapshot volume {r|rw}, the snapshot volume generally requires read-only, do not let the write operation

* The snapshot volume is on a logical volume and must be in the same volume group as the destination logical volume without specifying the volume group

ensure that the destination volume has sufficient space to accommodate the size of the snapshot volume

Example:lvreate–l512m–n mylv-snap–p r–s/dev/myvg/mylv

also ensure that directories mounted by/DEV/MYVG/MYLV are not modified by process access

method: Re-mount read-only

Mount–o REMOUNT,RO/DEV/MYVG/MYLV

Create a snapshot

re-mount for read-write

Mount–o REMOUNT,RW/DEV/MYVG/MYLV

Snapshot volume created successfully!

This article is from the "Aolens blocks until those" blog, be sure to keep this source http://aolens.blog.51cto.com/7021142/1439697