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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