Features/Ext4DefaultFs

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== Documentation ==
 
== Documentation ==
http://ext4.wiki.kernel.org
+
* http://ext4.wiki.kernel.org
http://kernelnewbies.org/Ext4
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* http://kernelnewbies.org/Ext4
  
 
== Release Notes ==
 
== Release Notes ==

Revision as of 20:58, 13 January 2009


Contents

Feature Name

Ext4DefaultFs

Summary

Replace ext3 with ext4 as the default filesytem for anaconda-driven installs.

Owner

  • email: sandeen@redhat.com

Current status

  • Targeted release: Fedora 11
  • Last updated: Jan-12-2009
  • Percentage of completion: 90%

Detailed Description

The ext4 filesystem has matured to the point where there is good e2fsprogs support, and upstream has shifted from "ext4dev" to "ext4." To broaden exposure, and make new ext4 features & performance more widely available, I propose that we make ext4 the default filesystem for new installs.

Benefit to Fedora

The ext4 filesystem has more features and generally better performance than ext3, which is showing its age in the Linux filesystem world. Features include:

  • Delayed allocation & mballoc allocator for better on-disk allocation
  • Sub-second timestamps
  • Space preallocation
  • Journal checksumming
  • Large (>2T) file support
  • Large (>16T) filesystem support (pending)
  • Defragmentation support (really pending)

I do not propose offering migration from ext3 by default, at this point, due to bugs in that process, and extra risk involved. Perhaps an "ext4migrate" boot option could be used to expose it for further testing.

Scope

This is mainly a simple (should be...) change for Anaconda's default choice. Anaconda already has ext4 support; it's a question of making it default now.

Bugs are sure to be found and exposed; these will require kernel & userspace fixes.

How To Test

As far as "Default install on ext4" is concerned, this is the same testing as is currently done for ext3 installs.

User Experience

User should notice generally better performance, and benefit from things like persistent preallocation when using updated torrent clients, etc.

Dependencies

Most is already in place; to some degree we depend on upstream fixing bugs and/or accepting bugfixes. But we have kernel+userspace today which supports ext4.

  • We should update grub to work on ext4; an untested, unintegrated patch exists. We could live with ext3 boot, but that would be less tidy.
  • livecd-tools will need some minor tweaks for ext4.

Contingency Plan

We can revert to ext3 as default if things go poorly.

Documentation

Release Notes

Comments and Discussion