ext4, or fourth extended file system, is a journaling file system for Linux. ext4’s most common use case is formatting volumes, hard drives, and other computing storage solutions.

ext4 is the default file system for DigitalOcean Volumes Block Storage due to its stability and backwards compatibility.

ext4 Articles

Partition volumes to divide a single storage device into smaller units that you can manage independently.
After you resize a partitioned volume to increase its available amount of disk, rewrite the partition table and expand the filesystem to use the new space.
Scale up the amount of storage space available on a volume.