Ext4 in Fedora 11

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= Frequently Asked Questions

Does GRUB support Ext4?

There is a patch in Red Hat Bugzilla to handle this. It has not been merged however for this release cycle due to lack of time for comprehensive testing and prioritization of other more important fixes. Since Fedora uses LVM by default and GRUB doesn't support it either, in practise, you will still need to continue using Ext3 filesystem for /boot partition. It is the recommended setup and that's how Anaconda sets it up by default. Anaconda will not let you format a /boot partition with Ext4 because of this.

I heard about data loss issues with delayed allocation and patches for that. Does Fedora include them?

Yes. They are headed upstream for 2.6.30 kernel and Fedora has backported those fixes to the 2.6.29 kernel in Fedora 11. They have been in the Rawhide development branch for the last few months now.

References:

http://lwn.net/Articles/326708/ http://lwn.net/Articles/322823/

How do I migrate from Ext3 to Ext4?

You can use the Anaconda boot option, "ext4migrate" to automatically migrate from Ext3 to the new Ext4 filesytem when upgrading from a previous release. If you do not use this option, Ext3 will be retained as your default filesystem

Do you still offer the choice of Ext3?

Yes. The regular DVD install image still lets you choose either Ext4, Ext3 or XFS. The Live CD/DVD images however use Ext4 and essentially transfer the entire image into the hard disk as part of the installation process and does not offer the ability to format the hard disk with any other filesystem. If you must choose a different filesystem, the regular DVD install image is recommended.

What about backward/forward compatibility?

The on-disk format (extends) for Ext4 is new and incompatible with the Ext3 on-disk format. Ext4 provides a number of performance and scalability improvements that were not possible with the older format used by Ext3. You can however use the Ext4 option to mount any Ext3 partition. Any new files is written will use the new format by default. If you want to get the other improvements from Ext4 but without changing the disk format, you can use the no extends mount option.