Slower performance with ext4

Fri Oct 30 18:54:11 UTC 2009

 Good references given. Google returns a lot of corruption hits but most are from Jan-March of this year. Those are related to write-caching which is always a risk in case of power failure or system hang (mentioned in most that I read). There was reference to a boot-time mount parameter as a "work around," which may have to do with disabling write-caching. This would definitely affect performance. I am still reading docs to see if that is indeed what has happened.

The document https://bugs.launchpad.net/ubuntu/+source/linux/+bug/453579 makes for very good reading (if you can stay awake). It includes discussion of whether or not to use ext4 as default in this release or revert to ext3. Some people wanted to stick to the traditional Debian conservatism and others (the Mavericks) sided with the bleeding edge. This was enlightening. The case was made that it was better to not take any chances and just use ext3. Then it was pointed out that of the corruption bug reports, there was no definitive link between the reports and they could not reproduce the error consistently enough to say that this component or that component/driver was defective. I found this to be the most revealing message:

  " The relation to that upstream bug is tenuous at best.  The upstream bug:

- is reported against a newer kernel than the one we're shipping

- is reported to only happen when ext4 is on top of the DM layer, whereas Scott's
      case was ext4 on a raw device

- is reported in connection with an unclean shutdown and subsequent
fsck,
      whereas Scott reported corruption of files without an unclean
shutdown 
      (but no mention in this bug of whether the corruption requires
an intervening 
      reboot/fsck to appear - Scott, please clarify)

   So that upstream bug link should be dropped; it really doesn't look like the same bug."

 So this was the reason for going ahead with the ext4 deployment depending on how you interpret what is being said here. I have to say that given how Linux is used and considering these docs, sticking with ext4 was a risky move. The decision may be vindicated if no bug is found with the file system itself. Distros always have to be wary of being last to roll out a feature. Why? Two words: Competitive Disadvantage.  I can't imagine that this is an easy decision for the guy who has to balance those two forces. I have to think that EULA's which absolve software companies of everything but dodging taxes play a big role in how these decisions are made, nicht wahr?

Regards, 

John

-----Original Message-----

From: Chan Chung Hang Christopher <christopher.chan at bradbury.edu.hk>

To: ubuntu-users at lists.ubuntu.com

Sent: Fri, Oct 30, 2009 3:35 pm

Subject: Re: Slower performance with ext4

Leonard Chatagnier wrote:

> --- On Fri, 10/30/09, Karl F. Larsen <klarsen1 at gmail.com> wrote:

>

>   

>> From: Karl F. Larsen <klarsen1 at gmail.com>

>> Subject: Re: Slower performance with ext4

>> To: "Ubuntu user technical support, not for general discussions" 

<ubuntu-users at lists.ubuntu.com>

>> Date: Friday, October 30, 2009, 7:38 AM

>> Leonard Chatagnier wrote:

>>     

>>> --- On Fri, 10/30/09, Karl F. Larsen <klarsen1 at gmail.com>

>>>       

>> wrote:

>>     

>>>> From: Karl F. Larsen <klarsen1 at gmail.com>

>>>> Subject: Re: Slower performance with ext4

>>>> To: "Ubuntu user technical support, not for

>>>>         

>> general discussions" <ubuntu-users at lists.ubuntu.com>

>>     

>>>> Date: Friday, October 30, 2009, 7:05 AM

>>>> Raphael wrote:

>>>>         

>>>>> Help, after I had clean installed Karmic on my

>>>>>           

>> ext4

>>     

>>>> partition, 

>>>>

>>>> the performance was significantly slower compared

>>>>         

>> to ext3.

>>     

>>>>    Startup was around 7 secs but

>>>>         

>> with ext4 it's now 20

>>     

>>>> secs 

>>>> application

>>>>

>>>>    speeds are also slower.

>>>>

>>>>

>>>>      If you can document this

>>>>         

>> in a bug report

>>     

>>>> it will help the 

>>>> designers of ext4 to work on their project to

>>>>         

>> speed it up.

>>     

>>>>      

>>>> I have been working on my wife's Windows XP and it

>>>>         

>> is sure

>>     

>>>> lazy coming on. They have an early Microsoft add,

>>>>         

>> and then

>>     

>>>> XP 

>>>> starts to unfold...

>>>>

>>>> Karl

>>>>

>>>>

>>>>         

>>> Karl, try reading the link the OP gave.  A bug

>>>       

>> report has already been filed.  Actually it was on data

>> loss as far as I read. 

>>     

>>> Leonard Chatagnier

>>> lenc5570 at sbcglobal.net

>>>

>>>

>>>       

>>     I did goto his bug report and the

>> responders seemed to change 

>> it to lost data. In his message he said ext3 was much

>> faster 

>> than ext4.

>>

>>

>>     

> It is a little confusing; subject vs. link.  However, I find Karmic much 

faster than ext3 on everything except browser surfing but that's not the same 

issue.

Saying weird things like Karmic (an OS) being faster than ext3 (a 

filesystem) just adds to the confusing.

Just do something like this: http://www.htiweb.inf.br/benchmark/fsbench.htm

For those interested, I have a tarball of fsbench (perl scripts emulated 

delivery to maildirs) if you wish to see filesystem performance when 

used for a mail store.

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