> BTW, Joshua, could you please let me know or give me any pointers for
> the reason why fsync=off option exists on PostgreSQL although PostgreSQL

A couple of reasons that I can think of. One would be data loads or
restoring from backup. Another would be on data that you can afford to
throw away.

> developers does not allow sacrificing data integrity ?
> If the reason is famous and clear in the community, I am sorry for
> bothering you.

No bother at all! We invite all good ideas and I am glad to see more
from our eastern community participate.

Another option you might want to look at to further give yourself a
boost in performance is full_page_writes.

Joshua D. Drake

> -- Hideyuki
> Joshua D. Drake wrote:
>> Hideyuki Kawashima wrote:
>>> Hello PostgreSQL Hackers,
>>> I have made a modification of PostgreSQL which accelerates INSERT/UPDATE 
>>> using UPS. The name of the software is "Sigres", and the philosophy is 
>>> considering a battery supplied memory as a persistent device instead of a 
>>> disk. You can download Sigres from http://sourceforge.jp/projects/sigres/ .
>>> In the maximum case, Sigres is 7 times faster than PostgreSQL default 
>>> (fsync=on) in my environment (CoreDuo 2.66GHz, UDMA/133), and it is also 
>>> 10% faster than PostgreSQL without fsync (fsync=off).
>> Interesting and what happens when the UPS fails? My main concern is that
>> one of the purposes of PostgreSQL is data integrity. I am all for every
>> performance enhancement we can achieve, that does *not* sacrifice that.
>> Sincerely,
>> Joshua D. Drake
>>> The magic lies in usually skipping XLogWrite() and ignoring WALWriteLock. 
>>> The exceptions are XLogWrite() calls from AdvanceXLInsertBuffer(). In 
>>> addition, in XLogFileClose() issue_xlog_fsync() before close(). (In this 
>>> point, Sigres is different from just simply setting fsync=off.)
>>> Although I think Sigres can be considered as one of the future directions 
>>> of PostgreSQL, I do not know whether this software can be accepted or not. 
>>> Could you please give me some comments ?
>>> Best Regards,
>>> -- Hideyuki Kawashima 
>>> Assistant Professor, University of Tsukuba
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