Ext4 is Coming!

[Michael]

Given the recent discussion on LKML two weeks ago, it is clear that many people feel they have a stake in the future development plans of the ext2/ext3 filesystem, as it one of the most popular and commonly used filesystems, particular amongst the kernel development community. For this reason, the stakes are higher than it would be for other
filesystems. The concerns that were expressed can be summarized in the following points:

http://lkml.org/lkml/2006/6/28/454

[Shadewalker]

There's still a long way to go. From the article:

At some point, probably in 6-9 months when we are satisified with theset of features that have been added to fs/ext4, and confident that thefilesystem format has stablized, we will submit a patch which causes thefs/ext4 code to register itself as the ext4 filesystem

Even though Reiser4 has been released, it hasn't been merged into the kernel yet, but I certainly hope it'll stabilize soon. I wonder if ext4 could actually compete with Reiser4 in terms of performance and flexibility?

[Rob Williams]

Time will tell. I'm actually surprised to hear about ext4. I didn't realize the limitations on ext3 though.

[Shadewalker]

As far as I understand, the amounts of concepts and (possible) patches for ext2/ext3 are just too overwhelming to be implemented in the current ext2/ext3 codebase, hence the best solution being an entirely "new" filesystem, even though it would share most of the fundamentals with its predecessors.

[Ethyriel]

This is great!

I've just been using XFS on everything I touch for a good combination of performance, stability, and lack of fragmentation. I'll probably stick with XFS for stores; but with extents, ext4 could be a very nice option for root partitions, if it's anywhere near as reliable as ext2 and ext3.

I gave up on Reiser ever since my Reiser3 filesystem at home started remapping files to directories.

[Shadewalker]

Originally Posted by Ethyriel

I gave up on Reiser ever since my Reiser3 filesystem at home started remapping files to directories.

Ouch, how'd that happen?

[Ethyriel]

Originally Posted by Shadewalker

Ouch, how'd that happen?

Well, it was a dirty unmount, but I've run into people since then who had the same thing happen. Dirty unmounts happen, things like this shouldn't. Especially with a journal to replay.

[Shadewalker]

Originally Posted by Ethyriel

Well, it was a dirty unmount, but I've run into people since then who had the same thing happen. Dirty unmounts happen, things like this shouldn't. Especially with a journal to replay.

I've been through a series of "dirty unmounts" and usually the worst thing that happened was that the partition wouldn't mount again before doing 'reiserfsck --rebuild-tree'. One time something weird happened which caused my /etc/passwd to disappear. Fortunately, there's always a local backup.

I'm strongly considering trying out JFS and/or XFS (especially JFS) at the moment. Anyone familiar with those? I've read some benchmarks and JFS looked appealing in particular.

[Ethyriel]

Originally Posted by Shadewalker

I've been through a series of "dirty unmounts" and usually the worst thing that happened was that the partition wouldn't mount again before doing 'reiserfsck --rebuild-tree'. One time something weird happened which caused my /etc/passwd to disappear. Fortunately, there's always a local backup.

I'm strongly considering trying out JFS and/or XFS (especially JFS) at the moment. Anyone familiar with those? I've read some benchmarks and JFS looked appealing in particular.

Well, I'm using XFS and it feels just as fast as Reiser3, if not faster. I only use ext2 for my /boot, everything else is XFS now. Yes, I do feel that ext3 is slower, but it's just my perception.

Linux filesystems not needing to be defragmented is pretty much a myth, but XFS's extents are so well implemented you can literally go 5 or 6 years on a high availability file server with almost no file fragmentation. I guess Reiser4 has similarly advanced extents, but it's reliability really isn't there yet.

Overall I feel more secure with it, but that also is impossible to quantify. However, I have an older system (over 6 years now) which has a tendency to hard freeze when I push it way too hard, so I have quite a few dirty unmounts. I haven't had any issues with XFS yet in about 6 months.

I haven't tried JFS, yet, but it's on my list. I'd also love to start playing with ZFS, but I suppose I'll need to install Solaris for that. I haven't gotten past downloading it, just yet.

[Michael]

A test version of Ext4 has now been released.

The experimental version has also been added to the 2.6.19 test kernel (see here).

If you want more information, there is a short write-up at Linux Watch.