Fedora 11 To Default To the Ext4 File System

ffs writes "The next release of Fedora, 11, will default to the ext4 file system unless serious regressions are seen, as reported by heise online. The LWN story has a few comments extolling the virtues of the file system. Some benchmarks have shown ext4 to be much faster than the current default ext3. Some of the new features that matter for desktop users are a faster file system check, extents support (for efficiently storing large files and reducing fragmentation), multiblock allocation (faster writes), delayed block allocation, journal checksumming (saving against power / hardware failures), and others. The KernelNewbies page has more information on each feature. As is the extfs tradition, mounting a current ext3 filesystem as ext4 will work seamlessly; however, most new features will not be available with the same on-disk format, meaning a fresh format with ext4 or converting the disk layout to ext4 will offer the best experience."

EXT4 in Clusters?

[BountyX]

After doing research on various cluster filesystems I eventually decided on GFS (as opposed to luyster, which seemed a bit overkill). How does EXT4 compare to GFS? Can EXT4 even be used in a clustered environment?

No

[Anonymous Coward]

Ext4 is not a SAN or distributed filesystem. GPFS/lustre/GFS remain a good choice for that.

Fresh format vs conversion

[MacColossus]

I read the article and it looks like converting from ext3 to ext4 may be problematic.

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.

Re:Why not ReiserFS?

[grumbel]

ReiserFS isn't actively maintained. In addition to that ext3 and now ext4 have learned quite a few new tricks since ReiserFS first appeared, you can now online resize an ext3 filesystem, it supports hashed b-trees, which should speed up directory handling, it is getting an online defrag tool and a bunch of other goodies. So many of the benefits that ReiserFS originally brought to the table can now be have with ext3 or ext4.

Re:So Ext4 in RH7 ?

[eparis]

It's already a technology preview in RHEL 5.3.

Re:A few answers

[eparis]

Yes you are missing something. :) The superblock on all extX say what features they support. So when you mount ext3 as ext4 the mount code can look what features that FS supports and use what new features it has available that won't break it as ext3. If you mount and ext3 fs as ext4 you'll get all of the benefits of ext4 like the enhanced inode allocator and what not, but you won't get extents so your huge file support is limited just like ext3) An ext4 fs can NOT be mounted as ext3 as the files will be stored using new features (like extents) which ext3 doesn't understand. Make sense? There will be (or is?) a conversion tool which will be able to downgrade ext4, but you can't just mount backwards.

Re:Why not ReiserFS?

[Anonymous Coward]

In fact suse changed their defaults from reiser to ext3 long time ago [opensuse.org]. The main reasons were: scalability on SMP, xattrs performance, lack of mainteinance, lack of a upgrade path...

Re:How does it compare to ext2?

[diegocgteleline.es]

is it possible to run ext4 without the journal?

Yes, it is [kernel.org]. And, as you can see in the link, ext4 is faster than ext2. Even with journaling.

Re:Ext4 small files performance?

[diegocgteleline.es]

You can see some of those benchmarks in this paper [fedoraproject.org] which explains the block allocator improvements that have been done in ext4.

Re:EXT4 in Clusters?

[Richard W.M. Jones]

Red Hat ship some web based tools called Luci and Ricci which basically do all of this, with a pointy-clicky interface.

Rich.

Re:EXT4 in Clusters?

[Forge]

I have used them.

1. The work for sharing a SAN but are not so useful for clustering local disks.

2. Even doing what they are good at, setup is a bit more tedious than I would like.

BTW: A nice setup menu dose not need to be GUI. Many of the console tools in the system-config-whatever series are nice.

Re:Fresh format vs conversion

[gzipped_tar]

Not always. If your old ext3 filesystem uses 128-bit inodes, they'll have to be converted to 256-bit by tune2fs. However, this may not be guaranteed to be successful. Actually it failed miserably on my system (it was several months ago and I don't know whether the e2fsprogs has been improved on this by now). I made backup before carrying out the experiment so after the failure I just reformatted the partition as ext4, updated fstab and recovered from backup.

Re:You Can Always Tell The Pioneers ...

[BTG9999]

Do you not know what Fedora is? Fedora is a bleeding edge distro. One that is openly acknowledged by Red Hat as being their Beta testers for new technologies that might eventually make it into RHEL. So this is just a standard thing Fedora does.

Re:FS choices in the Datacenter

[Per Wigren]

So turn it off the periodical fsck then:

tune2fs -c 0 -i 0 /dev/foo

It's perfectly safe as long as the underlying blockdevice is safe (RAID).

It WILL Help

[maz2331]

Ext4 is orders of magnitude faster than Ext3 regarding fsck time. Your half-day checks will almost certainly be reduced to minutes. The developers rewrote the algorithm to not require as intensive of a search in phase 1.

If it's really important to get the machines up in minimal time (even at risk of some data loss) then you can turn off the auto checks entirely.

Re:A few answers

[wiredlogic]

Actually, ext4 can be mounted as ext3 provided extents are disabled when creating the ext4 fs. This may be useful for someone who wants some of the new features of ext4 but needs to mount the media on a machine that can't be upgraded to support it.