What are the key differences between ext3 and ext4?
The main new features in ext4 are below, and are described more fully in New_ext4_features: • extent-mapped files for more efficient storage of file metadata (EXTENTS) • multi-block and delayed allocation for faster/better file allocations • support for larger filesystems (up to 2^48 blocks, currently 2^60 bytes) (64_BIT) • optimized storage of filesystem metadata like bitmaps and inode table (FLEX_BG) • less overhead for e2fsck, on-disk checksum of group descriptors (GDT_CSUM) • removed 32000 subdirectory limit (DIR_NLINKS) • nanosecond inode timestamps (EXTRA_ISIZE) In addition, use of a journal is optional and may be enabled or disabled with tune2fs and the “has_journal” option.
