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   lvmraid    ( 7 )

менеджер логических томов для объединения нескольких физических дисковых устройств в логический модуль (LVM RAID)

Описание (Description)

lvm(8) RAID is a way to create a Logical Volume (LV) that uses
       multiple physical devices to improve performance or tolerate
       device failures.  In LVM, the physical devices are Physical
       Volumes (PVs) in a single Volume Group (VG).

How LV data blocks are placed onto PVs is determined by the RAID level. RAID levels are commonly referred to as 'raid' followed by a number, e.g. raid1, raid5 or raid6. Selecting a RAID level involves making tradeoffs among: physical device requirements, fault tolerance, and performance. A description of the RAID levels can be found at www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf

LVM RAID uses both Device Mapper (DM) and Multiple Device (MD) drivers from the Linux kernel. DM is used to create and manage visible LVM devices, and MD is used to place data on physical devices.

LVM creates hidden LVs (dm devices) layered between the visible LV and physical devices. LVs in the middle layers are called sub LVs. For LVM raid, a sub LV pair to store data and metadata (raid superblock and write intent bitmap) is created per raid image/leg (see lvs command examples below).