Has anybody tried ext4?

Schwinni · Posted: Sun Oct 26, 2008 11:01 pm Post subject:

Have a look at the thread, I have exactly the same line in my log
The funny thing is that it only appears for my root partition.
For the home partition everything is normal.
If I wouldn't have a separate boot partition with ext2 I would say it is because grub doesn't handle ext4, but this way...
I really don't know what it is.

I also fscked my partitions now several times and everything seems to be fine.

I think I try to find out something about that message on the ext4 mailing list or on the IRC channel...

boris64 · Posted: Mon Oct 27, 2008 1:56 pm Post subject:

octoploid · n00b Joined: 21 Oct 2006 Posts: 65

devsk · Posted: Tue Oct 28, 2008 3:44 am Post subject:

is there a real world comparison of ext3 and ext4 somewhere? what I am interested in is:

1. large number of small files. How well does ext4 handle this case? space consumption and speed wise. This is one case where both speed can be increased and space consumption reduced like reiser4 does
.
2. small number of large files. e.g. how many fragments does the ext4 create for a 4GB file on a 70% used file system of 30GB? how fast is the delete of large files? Its slow on ext3/ext2.

3. there is no online de-fragmentation tool. Please don't flame me with "linux FSs don't fragment". Anybody who has created multiple virtual machines and have a full enough FS, knows that all FSs fragment.

These are the things that bother me on ext3. Does ext4 help with any of these?

wrc1944 · Posted: Tue Oct 28, 2008 8:14 am Post subject:

Here's some I just looked at:
http://www.linuxinsight.com/first_benchmarks_of_the_ext4_file_system.html

http://en.wikipedia.org/wiki/Ext4
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octoploid · n00b Joined: 21 Oct 2006 Posts: 65

Another up-to-date benchmark:

http://btrfs.boxacle.net/repository/single-disk/Initial-compare/Initial-Compare-Single_disk.html
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devsk · Posted: Thu Oct 30, 2008 7:05 am Post subject:

So, I tested ext4dev in 2.6.27.4. Stay away from it. Its worse than ext3 in every sense. Large files have many many (41 against 770) more fragments compared to ext3 (so, what's up with extents?). Seq write b/w drops 20%. And pdflush locks up cpu during large (5GB) file copy and kjournald2 goes into 'D' state, requiring a reboot. About the only thing going for it was that the delete of large files was much quicker than ext3. The tests were done on the same physical hardware and same partition, on an amd64 system.

lucke · n00b Joined: 11 May 2005 Posts: 35

They apparently fixed that bug with excessive number of extents. It's comparable to xfs now in this regard. All in all, it's dandy on .28.

octoploid · n00b Joined: 21 Oct 2006 Posts: 65

devsk · Posted: Thu Oct 30, 2008 3:33 pm Post subject:

may be the difference comes between ext4dev of 2.6.27.4 and ext4 of 2.6.28. But my experiments on the same hardware and partition under the same OS, same tools, same everything, paints ext4dev in bad shape. I will wait for 2.6.28 and see if it changes.

asturm · Developer Joined: 05 Apr 2007 Posts: 9280

That's because ext4dev != ext4

kernelOfTruth · Posted: Thu Oct 30, 2008 8:53 pm Post subject:

devsk · Posted: Thu Oct 30, 2008 11:32 pm Post subject:

agent_jdh · Veteran Joined: 08 Aug 2002 Posts: 1783 Location: Scotland

Schwinni · Posted: Fri Oct 31, 2008 9:20 am Post subject:

But be careful:
2.6.27-ext4-2 cannot patch "ext4/dir.c" because this file itself was patched from 2.6.27.3 to 2-6-27-4.
I didn't have the time to look at the rejected hunk yesterday.
The safest way is to wait for the next patch set (2.6.27-ext4-3).

Schwinni · 2.6.27-ext4-2

Seems like the failing hunk is included both in the kernel patch set for 2.6.27.4 and in 2.6.27-ext4-2:

From patch-2.6.27.4:

devsk · Posted: Sat Nov 01, 2008 12:24 am Post subject:

Schwinni · Posted: Sat Nov 01, 2008 12:55 am Post subject:

I don't know. At least on http://ext4.wiki.kernel.org/index.php/Ext4_patchsets it says

devsk · Posted: Sat Nov 01, 2008 1:35 am Post subject:

I got this reject while applying the patch:

devsk · Posted: Sat Nov 01, 2008 3:15 am Post subject:

OK, just booted with the patch and the tests on the same physical partition are much more favorable now. Number of fragments went down substantially. Sequential write/read b/w on large files went up beyond ext3 by 20%, I think mostly because of reduced number of fragments.

Had no effect on portage tree compared to ext2: same results, give or take few millisecs.

I can live with that.

Does anybody know anything about this error from bonnie++?

octoploid · n00b Joined: 21 Oct 2006 Posts: 65

devsk · Posted: Sat Nov 01, 2008 6:10 am Post subject:

doesn't apply on top of the other patch ext4-2. Did someone generate that patch against ext4-2?

edit: it applied with "patch -p1 -l". Cut&paste mangled the tabs.

fldc2 · Posted: Sat Nov 01, 2008 12:19 pm Post subject:

The only problem i've had with ext4 so far is that the torrents i download get lots of failed chunks for some reason, no matter what client is used, my workaround at this time is to download on a partition with a different filesystem

devsk · Posted: Sat Nov 01, 2008 4:39 pm Post subject:

ext4 is really shining with large files. I used to get upto 3000 fragments for a 650MB VM vmem file after repeated suspend/restore cycles. It has got stuck with 2 so far, which means suspend/resume of VM takes just 5-10 seconds, instead of worst cases 30-60 seconds. I just hope it doesn't oops on me.... :-)