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Re: [HACKERS] fsync method checking

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: josh(at)agliodbs(dot)com
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kurt Roeckx <Q(at)ping(dot)be>,Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>,pgsql-performance(at)postgresql(dot)org,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] fsync method checking
Date: 2004-03-18 20:49:20
Message-ID: 200403182049.i2IKnKK00246@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Josh Berkus wrote:
> Tom, Bruce,
> 
> > My previous point about checking different fsync spacings corresponds to
> > different assumptions about average transaction size.  I think a useful
> > tool for determining wal_sync_method has got to be able to reflect that
> > range of possibilities.
> 
> Questions:
> 1) This is an OSS project.   Why not just recruit a bunch of people on 
> PERFORMANCE and GENERAL to test the 4 different synch methods using real 
> databases?   No test like reality, I say ....

Well, I wrote the program to allow testing.  I don't see a complex test
as being that much better than simple one.  We don't need accurate
numbers.  We just need to know if fsync or O_SYNC is faster.

> 
> 2) Won't Jan's work on 7.5 memory and I/O management mean that we have to 
> re-evaluate synching anyway?

No, it should not change sync issues.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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