Slower performance with ext4

[Mark Kirkwood]

Mark Kirkwood wrote:
> Mark Kirkwood wrote:
>   
>> Christopher Chan wrote:
>>   
>>     
>>> Heh, what do you know? I have been burned by XFS after a powerloss and 
>>> got over 4000 zero length files in a postfix queue. No filesystem 
>>> corruption, just zero data files. You want to tell me that postfix does 
>>> not use fsync? You can guess what I did to the XFS filesystem mounted 
>>> for the queue directory. I destroyed it and got ext3 instead in full 
>>> data journal mode. Which I repeated on all the other mtas that had a XFS 
>>> filesystem for their mail queue.
>>>
>>>   
>>>     
>>>       
>> Hmm - not gonna get into trading personal insults , as nothing is to be 
>> gained that way.
>>
>> You were running this on server grade hardware? or - let me guess - a 
>> workstation with cheap sata drives? I have run many instances of mysql, 
>> postgres and oracle on *server* grade hardware [1] with xfs for probably 
>> the last 7 years and never have *any* data corruption issue in spite of 
>> many power outages...
>>
>> regards
>>
>> Mark
>>
>> [1] meaning a designated server mobo with eec ram and scsi (or sas) hard 
>> drives.
>>
>>
>>   
>>     
>
> Interesting data point for both of us:
>
> http://blogs.gnome.org/alexl/2009/03/16/ext4-vs-fsync-my-take/
>
> He claims ext4 is safe with sensible usage of fsync but reckons xfs is 
> not. Without wading through the code for the various fs it is tricky to 
> be 100% sure if he is correct or mistaken, as it is clearly *possible* 
> for the respective fs drivers to intercept the f(data)sync etc calls and 
> do undeserved violence to 'em....
>
> regards
>
> Mark
>
>
>   

Further, here is a posting about databases, xfs and fsync:

http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/

It reinforces what I've been saying - issues with device firmware can 
get you into trouble, these guys needed to disable the ssd write cache 
to guarantee reliability. Most database admins (including me) recommend 
battery backed raid controllers when used with sata drivers to be sure 
(no matter what fs is being used - or what operating system for that 
matter).

regards

Mark