Slower performance with ext4

[Christopher Chan]

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.