Core Storage

Core Storage is a logical volume management system on macOS that was introduced by Apple to Mac OS X Lion. Core Storage is a layer between the disk partition and the file system.

Core Storage is the basis for Apple's Fusion Drive technology, which presents several partitions on multiple drives as a single logical volume. It does this by using tiered storage, whereby it keeps the most frequently used blocks on the fastest storage device in the pool, which is, by default, an SSD.

Description
Apple CoreStorage defines four types of objects, instances of which are uniquely represented by a UUID:


 * Physical Volume (PV)
 * This is the actual physical storage device such as an internal hard drive or solid state drive. A PV is normally real media but it can be a disk image or even an AppleRAID Set. A disk offered to be a PV must be a partition and the encompassing scheme must be GPT.


 * Logical Volume Group (LVG)
 * This is the equivalent of volume groups in Linux LVM. The Logical Volume Group (LVG) is the top or "pool" level; zero or more may exist during any OS boot time session. An LVG exports zero or more Logical Volume Families (LVFs).


 * Logical Volume Family (LVF)
 * An LVF contains properties which govern and bind together all of its descendant Logical Volumes (LVs). These properties mainly provide settings for full disk encryption (such as whether the LVG is encrypted, which users have access, etc). An LVF exports one or more LVs.


 * Logical Volume (LV)
 * A logical volume exports a dev node, upon which a file system (such as Journaled HFS+) resides.