lvm2 - Logical Volume Manager administration tools​ 
LVM includes all of the support for handling read/write operations on physical volumes (hard disks, RAID-Systems, magneto optical, etc., multiple devices (MD), see mdadm(8) or even loop devices, see losetup(8)), creating volume groups (kind of virtual disks) from one or more physical volumes and creating one or more logical volumes (kind of logical partitions) in volume groups.

[root@localhost aleksej]# lvm help
Available lvm commands:
Use 'lvm help <command>' for more information

dumpconfig Dump active configuration
formats List available metadata formats
help Display help for commands
lvchange Change the attributes of logical volume(s)
lvconvert Change logical volume layout
lvcreate Create a logical volume
lvdisplay Display information about a logical volume
lvextend Add space to a logical volume
lvmchange With the device mapper, this is obsolete and does nothing.
lvmdiskscan List devices that may be used as physical volumes
lvmsadc Collect activity data
lvmsar Create activity report
lvreduce Reduce the size of a logical volume
lvremove Remove logical volume(s) from the system
lvrename Rename a logical volume
lvresize Resize a logical volume
lvs Display information about logical volumes
lvscan List all logical volumes in all volume groups
pvchange Change attributes of physical volume(s)
pvresize Resize physical volume(s)
pvck Check the consistency of physical volume(s)
pvcreate Initialize physical volume(s) for use by LVM
pvdata Display the on-disk metadata for physical volume(s)
pvdisplay Display various attributes of physical volume(s)
pvmove Move extents from one physical volume to another
pvremove Remove LVM label(s) from physical volume(s)
pvs Display information about physical volumes
pvscan List all physical volumes
segtypes List available segment types
vgcfgbackup Backup volume group configuration(s)
vgcfgrestore Restore volume group configuration
vgchange Change volume group attributes
vgck Check the consistency of volume group(s)
vgconvert Change volume group metadata format
vgcreate Create a volume group
vgdisplay Display volume group information
vgexport Unregister volume group(s) from the system
vgextend Add physical volumes to a volume group
vgimport Register exported volume group with system
vgmerge Merge volume groups
vgmknodes Create the special files for volume group devices in /dev
vgreduce Remove physical volume(s) from a volume group
vgremove Remove volume group(s)
vgrename Rename a volume group
vgs Display information about volume groups
vgscan Search for all volume groups
vgsplit Move physical volumes into a new or existing volume group
version Display software and driver version information

# On-line добавление/удаление жёстких дисков с помощью LVM

# pvcreate /dev/sda1 # наш эмулятор сбойного диска
Physical volume "/dev/sda1" successfully created

# pvcreate /dev/sdb1 # наш эмулятор спасательного диска
Physical volume "/dev/sdb1" successfully created

# vgcreate vg0 /dev/sda1 # создаем группу томов vg0
Volume group «vg0» successfully created

# lvcreate -n test -L10G vg0 #создаем раздел для «важной» инфы
Logical volume «test» created

# mkfs.ext2 /dev/vg0/test # создаем файловую систему на разделе

# mount /dev/mapper/vg0-test /mnt/tmp/ #монтируем раздел и заполняем его информацией.

# vgextend vg0 /dev/sdb1 # расширяем нашу группу томов на «спасательный» диск
Volume group «vg0» successfully extended

# pvmove /dev/sda1 /dev/sdb1 #передвигаем содержимое с «умирающего» диска на «спасательный»
/dev/sda1: Moved: 0.9%
/dev/sda1: Moved: 1.8%
…
/dev/sda1: Moved: 99.7%
/dev/sda1: Moved: 100.0%

# vgreduce vg0 /dev/sda1 # убираем «умирающий» диск из группы томов.
Removed "/dev/sda1" from volume group «vg0»

Итак:
Создаем логический раздел, форматируем его, монтируем и заполняем нужными данными, затем перемещаем раздел с одного устройства на другое, при этом раздел остается примонтирован и данные всё время доступны.