Ext3 and Ext4: Which file system to install?

[Sef]

Update: Ext4 is the default file system on Karmic Koala and beyond.

Disclaimer:- This thread only issues the use of Ext4 on Ubuntu Jaunty(9.04) and does not apply to earlier releases where Ext4 may not have been available as an option due to Ext4 not having been stable.

As you may have noticed, you now have the option of installing Ext4 through Ubuntu Jaunty. Ext4 is quite a big update from Ext3 but it still is only incremental and is backwards-compatible with Ext3, so it is very stable, however a few issues about the filesystem have recently sprung up that may require you to be a little careful when using this filesystem.

Reasons to stick to Ext3:-

1) Ext3 is the default file system for *buntus.

2) It is very stable, so no worries about losing your data due to crashes.

3) The one that is recommended to be on your work stations.


The issues with Ext4:-

1) There have been reports of crashes having corrupted configuration files and sometimes more with Ext4 in use.

2) This has been addressed in kernel 2.6.30, however it will not hit Ubuntu Jaunty, but Ubuntu Karmic.

3) 9.04 Release Notes: Other Known Issues for more detail.

Therefore, while Ext4 is really good, it still does need a few bugs to be ironed out, but all in all, it is quite stable for the average desktop user, just as long as you take regular backups, as you would when using any file system.

And just one more thing, Ext4 is not to be blamed completely, part of the problem stems from programs which fail to adhere to the standard regarding I/O on disk.

More information regarding this matter can be obtained here:
Theodore Tso's(One of Ext4's main developers) blog post regarding this issue:-
http://thunk.org/tytso/blog/2009/03/...-file-problem/

Article (29 May 2009): The Ext4 File Linux File System by Dr. Oliver Diedrich

(Thank you to PmDematagoda and bhodi.zazan for helping me improve this thread.)

[akrep55tr]

Thank you very much. This was a big question in my mind.

[Demonizer]

Ext4 cant be THAT bad .

[porchrat]

OK that is not great news, I thought the bugs had been ironed out, looks like I'm going to have to use ext3 in my new jaunty jackalope download

I had no idea there were so many issues, thanks for info Sef.

[vigyani]

B) Ext4 is beta:

1) Ext4 is the new still experimental (nonstable) file system for the *buntus.

2) It has been known to crash and data has been lost.

3) It is not for workstations that need a stable file system.

4) The current GRUB will not boot into it. A boot partition must be created.

5) Bugs are stil being worked out of it.

6) You have the time and enjoy reinstalling your os or oses, if it hoses your system. (To hose a system is to make the computer unbootable, so a reinstall is necessary.)

7) You frequently back up your system, so in case your data becomes unreadable due to a crash, you can replace it.

Yes, ext4 is faster than ext3, but do you really want to risk losing your data or having to reinstall *buntu and the other oses that are on your system or both?

Hi

It would be really nice if you can provide references and links to substantiate the claims made in this post.

[porchrat]

Hi

It would be really nice if you can provide references and links to substantiate the claims made in this post.

That is a good idea. I would like to read these articles as I have only been able to find benchmarks and positive press releases about ext4. It would be nice to read the other side of it.

From what I had read ext4 is marked "stable". I thought it was going to be the default filesystem of Ubuntu, but it seems like ext3 remains the default until at least 9.10.

I see what you mean about the lack of GRUB support, but that is OK as I always use a separate /boot partition anyway.

I am completely seduced by the speed of ext4 in the benchmarks, but if it going to be unpredictable I won't touch it.

[vividia]

I would like to read the source(s) about ext4. I'm still using ext3 and was considering making the leap.

[wanchai]

Here is something to read:
https://bugs.edge.launchpad.net/ubun...ux/+bug/317781
By the way, Theodore Ts'o is the author of ext4, he wrote some long posts in this thread that are worth reading.

For my system I decided to stay with ext3. I don't need to squeeze the last bit of performance out of my machines and I don't need to use the newest of the newest. Especially not if it's something as critical as a file system that cannot be easily downgraded.

[OmegaBLK]

I was just reading the release notes for 9.04 and there still are some issues with ext4 support that are not resolved as of the 9.04. Now an update will come when they are avaialable but, for now:

Lock-ups when deleting files from ext4 filesystems

In some cases, deleting files from an ext4 filesystem is reported to cause soft lock-ups in the kernel (330824). Investigation of this problem is ongoing, and it is expected that a fix for this problem will be made available as a post-release update. To avoid this problem, users may wish to install using the default ext3 filesystem and convert their filesystem to ext4 (as documented on the ext4 wiki) once a fix is available.

Switching to ext4 requires manually updating grub

If you choose to upgrade your / or /boot filesystem in place from ext2 or ext3 to ext4 (as documented on the ext4 wiki), then you must also use the grub-install command after upgrading to Ubuntu 9.04 to reinstall your boot loader. If you do not do this, then the version of GRUB installed in your boot sector will not be able to read the kernel from the ext4 filesystem and your system will fail to boot.

Possible data-loss problems resizing ext4

The resize2fs tool may cause data loss when growing or shrinking ext4 filesystems off-line. See this mail from the upstream maintainer for more details. Unfortunately we became aware of this too late to fix it in Ubuntu 9.04. If you wish to resize an ext4 filesystem using the tools in Ubuntu 9.04, you may be able to work around these problems by first disabling the flex_bg and uninit_bg features (do not attempt this on a mounted filesystem!):

tune2fs -O ^flex_bg,^uninit_bg /dev/DEVICE_NAME
e2fsck /dev/DEVICE_NAME

However, we still strongly recommend taking significantly more care with backups than usual before attempting to resize an ext4 filesystem.

source

[aniruddha]

Awesome stuff, thank you for all the clarifications. And here I was really looking forward to ext4 too. So it goes...