Therefore, it is recommended to select a section size in the initial setting , Don't change it in the future. Different section sizes mean different VG Particle size. Physical to logical mapping. Its purpose is to map devices —— LVM2 You have to use this module. If this module is not enabled , So right. The function of the device mapper is to map these names correctly to the physical device.
Often used lvm 8 Command to access volume groups. The device mapper module must be loaded at system startup. Again , Distributions are often responsible for this —— In the installation LVM2 Packet time , They are often rebuilt or updated initrd image , Add appropriate kernel modules and startup scripts.
Different distributions determine whether the root file system is in a volume group in different ways. See the release documentation for details. If you're not sure , You need to check initrd or initramdisk Configuration of. In practical use , A logical volume behaves like a block device , For example, you can use it as the original partition of the database. It's very easy to expand volumes. If there is enough free space in the volume group , Then just use lvextend To expand the volume , No need to unload it.
If VG There's not enough space in the game , So first you need to add more physical disks. Depending on the file system type , This operation can be performed online while the file system is mounted. For these cases , have access to pvmove, It can release online PV, This makes it easy to replace them.
If you want to release one PV In order to replace , Then it's better to ban its distribution , This ensures that it remains idle until it is removed from the volume group. You can also use -b Parameter to move the operation to the background.
In the background , Status reports are sent to the system log. If the data does not change during the backup process , Then you can get a consistent backup.
If you don't stop the system during the backup , It's hard to guarantee that the data doesn't change. By using snapshots , You can get the same LV Two copies of —— One can be used for backup , The other continues to be used in daily operations. For all daily operations , The snapshot looks like primary LV A copy of. In this order ,ro Flag means mount it as read-only. Can be in lvcreate Add After the order -p r, That's right. LVM Level makes it read-only.
If LV No file system , Or you need an original backup , You can also use it directly on this device node dd. This script is not suitable for the enterprise environment ; In an enterprise environment , Incremental backup with history is more appropriate , But the concept is the same. In some special cases , The backup cycle cannot be estimated or the replication process is long , So the script can use lvdisplay Inquire about Snapshot CoW And extend this as needed LV. In the use of LVM2 when , Snapshots can not be read-only.
It means , After creating the snapshot , You can mount and read and write snapshots just like regular block devices. After these steps , Then users can access the virtual machine they just created. You can also automate these steps with a script. Current LVM2 Development results provide high availability for logical volumes. A physical volume can belong to at most one VG.
A physical volume is assigned to a volume group as a whole. The storage space in the physical volume is divided into physical partitions PP. They belong to the same VG On all the disks of , The size of the physical partition is exactly the same. In each volume group , You can define one or more logical volumes LV. From the perspective of users , The data stored on the logical volume seems to be continuous , But it can be spread across different physical volumes in the same volume group.
A logical volume consists of one or more logical partitions LP form. Each logical partition has at least one corresponding physical partition. A logical partition and a physical partition always have the same size. Up to three copies of data can be located on different physical partitions. Usually , To achieve redundancy , Locate physical partitions that store the same data on different physical disks.
Data in logical volumes can be stored in an organized way , And has the form of a file located in a directory. This structured and hierarchical form of organization is called a file system. You can also treat the data in a logical volume as a continuous string of bytes. This type of logical volume is called the original logical volume. It's the responsibility of the application to use this data to access and interpret it correctly.
Volume group descriptor area VGDA It's an area on the disk , It contains information about the volume group that the physical volume is in. It also includes information about the properties and status of all physical and logical volumes that belong to the volume group. Today HDDs are typically aggregated into arrays in storage appliances using various methods to provide redundancy in case of the failure of any single HDD.
In this case the array, or a portion of the storage space in the array, will be presented to a client operating system as a Logical Unit LUN. This is not yet LVM, however, as the LUN still appears to the operating system as a single, large-capacity storage device. LVM use arises when we consider how the client operating system is going to subdivide the space in a disk for its use. This subdivision is necessary as disk space may be needed for different things such as page space, file systems, a kernel dump device, or possibly raw data space for an application that does not want to use files to store its data.
The majority of disk space is normally used for file storage, and there are many reasons to implement multiple file systems to store data in categories that are best handled differently. Each file system will then need to have space allotted from the disks available. Early operating systems solved this problem by disk partitioning.
This involved dividing each disk into a few fixed-size partitions, whose beginning and end points were defined by a partition table written to a reserved portion of each disk.
This worked, but had limitations. The size of the partition table typically limited the number of partitions to eight or less. Digitalocean Community. Docker Community. Fortios Community. General Guides Plugin Index Community. Google Community. Grafana Community.
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