The ext4 or fourth extended filesystem is a journaling file system for Linux, developed as the successor to ext3. The ext4 filesystem can support volumes with sizes up to 1 exbibyte (EiB) and files with sizes up to 16 tebibytes (TiB). Extents replace the traditional block mapping scheme used by ext2 and ext3. An extent is a range of contiguous physical blocks, improving large file performance and reducing fragmentation. A single extent in ext4 can map up to 128 MiB of contiguous space with a 4 KiB block size.