During an in-place upgrade of a CentOS 7 file server, a systems administrator must convert a 2 TB /data partition that is currently formatted as ext3 to a file system that (1) keeps journaling for quick crash recovery, (2) uses extents and delayed allocation to reduce fragmentation, and (3) can be upgraded without first copying the data off the disk. Which file system type will satisfy all of these requirements?
The fourth extended file system (ext4) is backward-compatible with ext3, letting an administrator enable new features on an existing ext3 partition with tools such as tune2fs and e2fsck rather than re-creating the file system. Ext4 retains a journal for crash recovery, adds extent-based allocation, and implements delayed allocation to improve performance and reduce fragmentation. Ext2 lacks journaling, so it fails the recovery requirement. XFS offers journaling and extents but cannot be converted from an ext3 partition in place; the disk must be reformatted and the data migrated, which violates the upgrade constraint. While a utility exists to convert an ext3 partition to Btrfs, ext4 is the direct successor and the intended upgrade path that satisfies all requirements seamlessly.