Host Architectures File Systems & File System Protocols
Systems Architecture File System Application Database File System HBA Volume Manager
Kernel I/O Driver
SAN Disk Controller Volume Manager Driver
File systems either access storage devices directly or access virtual disks presented by a Logical Volume Manager (LVM).
Database management systems typically store data either in container files, in managed volumes that they perceive as disks, or directly on disks or disk partitions.
Logical Volume Managers were originally targeted to provide RAID functionality in situations where it was not possible or desirable to use hardware RAID controllers.
The volume manager, as a server software component, forms a layer between file systems and HBA drivers. The main purpose of volume managers is to virtualize whatever the server perceives as physical disk drives, presenting it in a form more convenient for file system use.