Block devices in computer operating systems typically correspond to disks or
disk partitions, and are used to store files in a filesystem. Disks are not the
only real or virtual device which adhere to the block accessible stream of
bytes block device model. Files, remote devices, or even RAM may be used as a
virtual disks. This article examines several common combinations of block
device layers used as virtual disks in the Linux operating system: disk
partitions, loopback files, software RAID, Logical Volume Manager, and Network
Block Devices. It measures their relative performance using different
filesystems: Ext2, Ext3, ReiserFS, JFS, XFS,NFS