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I'm going to upgrade from Ubuntu 9.04 to Ubuntu 9.10 in a near future and wanted to know if I should migrate my existing ext3 partitions to ext4 during the process and, if yes, why?

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Because every FS is bug proof at first "stable" release? Wait, no. As someone who has been bitten by being an early adopter of file systems a bunch of times, I would suggest waiting until someone else looses a bunch of data to some corner case. In fact, I would suggest waiting for a few of those. – Bill Weiss Oct 9 '09 at 14:18
However, why wait? You can upgrade to XFS right now, and get most of the features of ext4, along with some bonus ones :) – Bill Weiss Oct 9 '09 at 14:25
@Bill Well, I guess Ext4 was considered stable in Jaunty. So it's not really a first stable release. However, I'm not sure many people used it and totally agree with your advice (waiting for some people to loose data). BTW, XFS could be indeed a good idea. Thanks. – Pascal Thivent Oct 9 '09 at 22:41

Ext4 Howto has some information about the features of ext4. Looks over benchmarks find ext4 faster than ext3, though it's not required to turn on all of the new features.

Honestly, you could mount your ext3 partitions with ext4 and take a taste of ext4 without needing to use all the new features. You'll have the ability to go back to ext3.

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Thanks for the answer. However, I've read somewhere: "Ext4 is backward compatible with the ext3 disk format so all you need to do is to mount your ext3 filesystem as ext4 (edit /etc/fstab and reboot). You can later use tune2fs to turn on new ext4 features, but then you need to do a full fsck and wont be able to mount the filesystem as ext3 any more. Only new files created will use the extents feature though.". I'm not sure I'll do this move for now. – Pascal Thivent Oct 9 '09 at 13:47
up vote 1 down vote accepted

Ok, according to this blog post introducing new features of Karmic Koala:

Ext4 filesystem was introduced in Jaunty. In Karmic, it has graduated to become the default filesystem. Like the GRUB 2 bootloader, the ext4 filsystem will only be applied for new installation. Existing users who are still on Ext3 will remain as Ext3 unless you choose to upgrade to Ext 4 manually.

So, I won't have to choose during the upgrade from Jaunty to Karmic itself. That's actually a good thing.

Then, I followed the given link describing how to upgrade to ext4 manually and, having read the whole post including comments:

  1. I'm a bit scared
  2. I'm not sure all applications are ready for ext4,
  3. I don't think the benefits are worth the upgrade in my case.

I will thus patiently wait before to upgrade to ext4.

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