Understanding LVM

LVM (Logical Volume Management) パーティションには利点がいくつもあります。LVMパーティションは physical volumes としてフォーマットされます。一つまたはそれ以上のボリュームが結合して volume group を形成します。お互いにボリュームグループの合計ストレージが分割されて一つまたはそれ以上の logical volumes になります。論理ボリュームはまるで標準パーティションのように動作します。そして ext4 またはマウントポイントのようなファイルシステムを持ちます。

To understand LVM better, imagine the physical volume as a pile of blocks. A block is a storage unit used to store data. Several piles of blocks can be combined to make a much larger pile, just as physical volumes are combined to make a volume group. The resulting pile can be subdivided into several smaller piles of arbitrary size, just as a volume group is allocated to several logical volumes.

An administrator may grow or shrink logical volumes without destroying data, unlike standard disk partitions. If the physical volumes in a volume group are on separate drives or RAID arrays then administrators may also spread a logical volume across the storage devices.

You may lose data if you shrink a logical volume to a smaller capacity than the data on the volume requires. To ensure maximum flexibility, create logical volumes to meet your current needs, and leave excess storage capacity unallocated. You may safely grow logical volumes to use unallocated space, as your needs dictate.