The article describes basic LVM architecture and administration
LVM components:
Clustered LVM architecture:
Logical volumes created with CLVM on shared storage are visible to all computers that have ac-cess to the shared storage.
The underlying physical storage unit of an LVM logical volume is a block device such as a parti-tion or whole disk. To use the device for an LVM logical volume the device must be initialized asa physical volume (PV). Initializing a block device as a physical volume places a label near thestart of the device.
Physical volumes are combined into volume groups (VGs). This creates a pool of disk space outof which logical volumes can be allocated.Within a volume group, the disk space available for allocation is divided into units of a fixed-sizecalled extents. An extent is the smallest unit of space that can be allocated, Within a physicalvolume, extents are referred to as physical extents
A volume group is divided up into logical volumes. There are three types of LVM logicalvolumes:linearvolumes,stripedvolumes, and mirroredvolumes.
A linear volume aggregates multiple physical volumes into one logical volume. For example, ifyou have two 60GB disks, you can create a 120GB logical volume. The physical storage is con-catenated.
Striping enhances performance by writing data to a predetermined number of physical volumesin round-round fashion. With striping, I/O can be done in parallel:
A mirror maintains identical copies of data on different devices. When data is written to one device, it is written to a second device as well, mirroring the data. This provides protection for device failures. When one leg of a mirror fails, the logical volume becomes a linear volume and can still be accessed
CLI examples.
Create physical volume:
pvcreate /dev/hdb1
pvcreate /dev/sdd1 /dev/sde1 /dev/sdf1Scan for block devices:
lvmdiskscan