ext3 data=ordered - good enough for oracle?

[Herta Van den Eynde]

Johann Lombardi wrote:
>>Given that the default journaling mode of ext3 (i.e. ordered), does not 
>>guarantee write ordering after a crash, is this journaling mode safe 
>>enough to use for a database such as Oracle?  If so, how are out of sync 
>>writes delt with?
> 
> 
> Oracle manages its own I/O cache in userspace and handles data coherency related
> to that. So data=journal is useless in this case.
> I guess databases such as Oracle uses O_SYNC to control the flushing of data 
> or even O_DIRECT to bypass the kernel cache.
> 
> Johann
 >
Thanks for the reply, Johann, but given that Oracle is still using the 
filesystem (unless you use raw devices or ASM), what good does caching 
do in case of a hard crash?
The O_SYNC and O_DIRECT would help.  Is there any way to verify that 
this is what Oracle actually does?

(Reason I'm asking is that I had a number of corruptions during the past 
year, and I have better things to do at nights than restoring databases.)

Kind regards,

Herta



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