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Re: ext3 data=ordered - good enough for oracle?



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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