Slower performance with ext4

Rashkae ubuntu at
Mon Nov 2 00:19:08 GMT 2009

Chan Chung Hang Christopher wrote:
> fyrbrds at wrote:
>>   >Data loss anyone?<
>> What evidence do you have that there would be data loss? ext2 and ext3 were used almost immediately after their release as well. The distro maintainers usually do some basic reliability tests or at least have access to such tests. So I would be happy to read any tests you've seen that suggest ext4 is unreliable. To start scaring people with talk of data loss based on random speculation would not be good. 
> Dude, I used to work with clusters of mta boxes. The last thing I needed 
> then was a filesystem that loses data or corrupts its metadata easily. I 
> wait before using any new fangled filesystem regardless of how uber fast 
> it is or I play the pull the plug game with them with whatever 
> journaling mode they have available.
> ext4 data loss reports started with Ubuntu Jaunty I think too?

The early data loss in Jaunty was really applications clobbering their
own files combined with EXT4's delayed allocation.  Basically, EXT4 was
behaving, for all intents and purposes, like XFS, without the null
bytes.  (I still question the sanity of whoever thought this would be a
good idea.. after all, wouldn't be all be using XFS years ago if this
behaviour was so superior?)  Following patches back ported to change
that introduced kernel soft lock bug in the ubuntu kernel (that was
never confirmed in the mainline kernel.).  And now we have uncomfired
sightings of data corruption, but the one person who claims to reproduce
that looks like he has memory corruption issues.  (He gets a different
md5sum every time he checks the same file... not really a filesystem
issue there.)

None of this is really applicable to your point.  for a mission critical
production system, you want to use what's known and proven (I do find
the choice of jfs odd however.  I like EXT3 for reliable and
predictable, and XFS for performance, so long as I know my particular
workload won't be affected by XFS's null bytes on unclean shutdown.)

However, the improvements EXT4 has made to the workloads that caused
EXT3 bad performance are amazing.. I'm much looking forward to the
testing/proving phase to be done.

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