Btrfs (pronounced as "better F S",[9] "butter F S",[13][14] "b-tree F S",[14] or B.T.R.F.S.) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused with Linux's LVM), developed together. It was founded by Chris Mason in 2007[15] for use in Linux, and since November 2013, the file system's on-disk format