Editing Ext2 (section)

==File-system limits==
{| class="wikitable" style="float:right; margin:0.5em 0 0.5em 1em"
|+ Theoretical ext2 limits under Linux<ref>{{Cite web |title=File system guide |url=http://linuxreviews.org/sysadmin/filesystems/ |url-status=dead |archive-url=https://web.archive.org/web/20110917065413/http://linuxreviews.org/sysadmin/filesystems/ |archive-date=2011-09-17 |access-date=2008-01-24 |publisher=Linux Reviews}}</ref>
|-
!align="left" | Block size:
|align="right" | 1 KiB
|align="right" | 2 KiB
|align="right" | 4 KiB
|align="right" | 8 KiB
|-
!align="left" | max. file size:
|align="right" | 16 GiB
|align="right" | 256 GiB
|align="right" | 2 TiB
|align="right" | 2 TiB
|-
!align="left" | max. filesystem size:
|align="right" | 4 TiB
|align="right" | 8 TiB
|align="right" | 16 TiB
|align="right" | 32 TiB
|}

{{original research|bit|reason=There are lots of calculations and numbers, all unsourced. (Can ext2 even have a 512-byte block size?)|date=December 2021}}

The reason for some limits of ext2 are the file format of the data and the operating system's kernel. Mostly these factors will be determined once when the file system is built. They depend on the block size and the ratio of the number of blocks and inodes.{{citation needed|date=December 2021}}
<!-- TODO: research about the following limits in Kernel 2.6 -->
In Linux the block size is limited by the architecture [[page size]].<!--Block sizes of 8nbps;KiB are only possible on alpha-architectures by default. -->

There are also some userspace programs that cannot handle [[Large file support|files larger than 2&nbsp;GiB]].

If ''b'' is the block size, the maximal file size is limited to min( ((''b''/4)<sup>3</sup> + (''b''/4)<sup>2</sup> + ''b''/4 + 12) × ''b'', (2<sup>32</sup> − 1) × 512 ) due to the i_block structure (an array of direct/indirect EXT2_N_BLOCKS) and i_blocks (32-bit integer value) representing the number of 1024 byte (1 kilobyte)<ref>{{Cite web |title=Creating the Ext2 Filesystem - Understanding the Linux kernel, Second edition |url=https://www.oreilly.com/library/view/understanding-the-linux/0596002130/ch17s04.html |access-date=25 July 2023 |website=www.oreilly.com}}</ref> "blocks" in the file.{{or|date=December 2021}}

The maximal number of sublevel-directories is 31998, due to the link-count limit.{{citation needed|date=December 2021}}  Directory indexing is not available in ext2, so there are performance issues for directories with a large number of files (>10,000).  The theoretical limit on the number of files in a directory is 1.3 × 10<sup>20</sup>,{{or|date=December 2021}} although this is not relevant for practical situations.

Note: In Linux 2.4 and earlier, block devices were limited to 2&nbsp;TiB, limiting the maximal size of a partition, regardless of block size.<ref>{{Cite web |title=The Second Extended File System |url=https://cscie28.dce.harvard.edu/lectures/lect04/6_Extras/ext2-struct.html |access-date=2024-12-07 |website=cscie28.dce.harvard.edu}}</ref>