will issue a warning if that mount option is used. There are also some disks that do not properly implement the write cache flushing extension necessary for barriers to work, which causes a similar warning. In these situations, where barriers are not supported or practical, reliable write ordering is possible by turning off the disk's write cache and using the mount option. Turning off the disk's write cache may be required even when barriers are available. Applications like databases expect a call to fsync() to flush pending writes to disk, and the barrier implementation doesn't always clear the drive's write cache in response to that call. There is also a potential issue with the barrier implementation related to error handling during events, such as a drive failure. It is also known that sometimes some virtualization technologies do not properly forward fsync or flush commands to the underlying devices (files, volumes, disk) from a guest operating system. Similarly, some hard disks or controllers implement cache flushing incorrectly or not at all, but still advertise that it is supported, and do not return any error when it is used. There are so many ways to handle fsync and write cache handling incorrectly, it is safer to assume that cache flushing does not work unless it is explicitly tested, regardless of how reliable individual components are believed to be. Near-time extinction due to date-stamp limitation Ext3 stores dates as Unix time using four bytes in the file header. 32 bits does not give enough scope to continue processing files beyond January 18, 2038 - the Year 2038 problem. ext4 On June 28, 2006, Theodore Ts'o, the principal developer of ext3, announced an enhanced version, called ext4. On October 11, 2008, the patches that mark ext4 as stable code were merged in the Linux 2.6.28 source code repositories, marking the end of the development phase and recommending its adoption. In 2008, Ts'o stated that although ext4 has improved features such as being much faster than ext3, it is not a major advance, it uses old technology, and is a stop-gap; Ts'o believes that Btrfs is the better direction, because "it offers improvements in scalability, reliability, and ease of management". Btrfs also has "a number of the same design ideas that reiser3/4 had". See also List of file systems Comparison of file systems Extended file attributes Ext2Fsd Next3, modified version of ext3 which snapshots References