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



Thanks for your replies and pointers, Johann and Zach. I hope to find time next week to study the extra information.

Kind regards,

Herta

Zach Brown wrote:
Herta Van den Eynde 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?


Yes, the database doesn't rely the kind of functionality that
data=journaled provides that data=ordered doesn't.  data=ordered is fine.


If so, how are out of sync writes delt with?


The database, just like ext3/jbd, implements its own consistency
mechanisms by careful write ordering.  ext3 uses in-kernel device APIs
to issue writes and find out when they're on disk, the database ideally
uses O_DIRECT.

I looked around otn.oracle.com to find a doc that talks about
configuring and verifying AIO+O_DIRECT in the database but got tired of
searching.  You might be able to find something if you're more patient
than I was.

- z


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