1 .. SPDX-License-Identifier: GPL-2.0
6 An ext4 file system is split into a series of block groups. To reduce
7 performance difficulties due to fragmentation, the block allocator tries
8 very hard to keep each file's blocks within the same group, thereby
9 reducing seek times. The size of a block group is specified in
10 ``sb.s_blocks_per_group`` blocks, though it can also calculated as 8 \*
11 ``block_size_in_bytes``. With the default block size of 4KiB, each group
12 will contain 32,768 blocks, for a length of 128MiB. The number of block
13 groups is the size of the device divided by the size of a block group.
15 All fields in ext4 are written to disk in little-endian order. HOWEVER,
16 all fields in jbd2 (the journal) are written to disk in big-endian
19 .. include:: blocks.rst
20 .. include:: blockgroup.rst
21 .. include:: special_inodes.rst
22 .. include:: allocators.rst
23 .. include:: checksums.rst
24 .. include:: bigalloc.rst
25 .. include:: inlinedata.rst
26 .. include:: eainode.rst