data=journal
also: full journaling
An ext4 filesystem mount option that writes all data and metadata to the journal before committing to the main filesystem, providing maximum data integrity at the cost of performance.
data=journal is a journaling mode for ext4 filesystems that ensures the highest level of crash safety. When enabled, the filesystem writes both file data and metadata to the journal first, then commits it to the actual filesystem afterward.
This approach prevents data corruption and loss during unexpected power failures or system crashes, since the journal provides a recovery checkpoint. However, it significantly reduces write performance because every data write effectively happens twice—once to the journal and once to the filesystem.
Example: mount -o data=journal /dev/sda1 /mnt mounts an ext4 partition with full journaling. This is commonly used on mission-critical systems or databases where data integrity is more important than speed.
Other journaling modes like data=ordered (default) and data=writeback offer faster performance with varying levels of safety.