Slower performance with ext4

[Christopher Chan]

Ong Raphael wrote:
>
> So, is the conclusion that ext4 sucks and ext3 rocks in performance wise?

I do not know the answer to that because I have not looked at how ext4 
behaves. Performance wise, if you are not using hardware raid with bbu 
cache, ext3 in data=journal mode and with its journal stored externally 
on a bbu nvram card will blow XFS out of the water and still guarantee 
data and metadata consistency.

> ------------------------------------------------------------------------
> *From:* Christopher Chan <christopher.chan at bradbury.edu.hk>
> *To:* "Ubuntu user technical support, not for general discussions" 
> <ubuntu-users at lists.ubuntu.com>
> *Sent:* Monday, 2 November 2009 1:49:48
> *Subject:* Re: Slower performance with ext4
>
> Mark Kirkwood wrote:
> > Christopher Chan wrote:
> > 
> >> Journaling only for metadata is not 'as much journaling as any other
> >> canditates.' You cannot say metadata journaling only as equivalent to
> >> the data and metadata journaling that is possible with ext3. XFS's
> >> journaling only provides filesystem metadata consistency which is why
> >> you get files full of NULLs after a crash/power out. MTAs rely on 
> fsync
> >> calls and how a filesystem behaves in regards to fsync requests is the
> >> real determiner of whether there is a data guarantee or not. XFS does
> >> not provide data guarantee. It, at best, provides a metadata 
> guarantee.
> >> XFS should not be used for mta queues unless it is in conjunction with
> >> hardware raid that has a bbu cache. XFS is best suited for streaming
> >> applications where the data loss is tolerated.
> >>
> >> 
> >>   
> > Sorry, but that is completely incorrect. Applications that use fsync 
> are
> > safe with any filesystem - fsync forces the modified buffers to *disk*,
> > so all discussions about os and filesystem caching are irrelivant[1].
> > 
>
> Yes...where *disk* = journal. Which for JFS, XFS and ext3 data=ordered
> means metadata only. Only ext3 data=journal guarantees data and
> metadata. Feel free to get (whoever filesystem developer) to confirm for
> me because you won't get any other answer than what I have just posted.
>
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