Tuning for PostGreSQL Database

[Simon J Mudd]

jim at nasby.net ("Jim C. Nasby") writes:

> > On Sat, 19 Jul 2003, Tom Samplonius wrote:
> > > Softupdates on, async off.  Softupdates is just a better async.
> > 
> > postgresql fsync's all its files before returning from a commit in order
> > to ensure durability, right?  Does softupdates interfere with the
> > functioning of sync(2)/fsync(2)?
>  
> No, afaik it only fsync's the write-ahead-logs.

Someone else mentioned Qmail. I use Postfix and I know the author
relies on fsync semantics before confirming the acceptance of email.
I'm sure Qmail (and sendmail, ...) does the same.  They should do -
the RFC requires this (that mail can't be lost once it is accepted for
delivery).

Therefore I think we are confusing 2 different issues.  The effect of
soft-updates (which tries to reorder writes to ensure FS recover is
easier) and sync/fsync which only returns when the FS or file have
been flushed to disk.

I would guess that PostGreSQL uses fsync() and softupdates do not
effect the fsync() semantics.

Or am I missing something?

Simon