By way of Heise Online comes more detailed information about what's causing some to lose data in systems using the new ext4 file system. The ext4 file system, which is slated to eventually replace ext3 as the default file system of choice in many Linux distributions, can experience significant data loss after system crashes or unclean shutdowns.

Ted Ts'o, Linux Foundation's CTO and maintainer of the ext4 file system, says that the loss is due to how ext4 writes to disk. He says ext4, and newer file systems such as XFS and Btrfs, use delayed allocation. This means that writing data to disk can take up to a minute (compared to ext3's write time of about five seconds). The longer write time improves system performance and organization of data on the hard drive. Ts'o says that the ext4 team is working out a solution, but it's an issue that would benefit from being addressed from all angles.

The majority of computer users don't spend much time thinking about the file system their operating system uses. Granted, people installing alternative operating systems might give more consideration to the available file systems than the general population -- unless there's a specific need for a certain file system, many go with their distribution's default option.

While your file system type isn't something you should need to think about regularly, and making an informed choice for machines with specialized, dedicated tasks is important, usually choosing the default file system type for your operating system is fine. Several Linux distributions (including Fedora and Ubuntu) are planning to move their default file systems from ext3 to ext4 in upcoming releases, while a number of distributions already (or will soon) support ext4 as a file system option.

IBM has a (rather surprisingly) interesting look at what's different about the ext4 file system, including details on why some changes were made, and how moving from ext3 to ext4 works.