RE: AW: AW: AW: WAL does not recover gracefully from ou t-of -dis k-sp ace

From: "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM>
To: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: RE: AW: AW: AW: WAL does not recover gracefully from ou t-of -dis k-sp ace
Date: 2001-03-10 02:31:36
Message-ID: 8F4C99C66D04D4118F580090272A7A234D330B@sectorbase1.sectorbase.com
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> $ gcc -Wall -O -DINIT_WRITE -DUSE_DSYNC -DBLOCKS=1 tfsync.c
^^^^^^^^^^^
You should use -DUSE_OSYNC to test O_SYNC.
So you've tested N * write() + fsync(), exactly what I've asked -:)

> So I also see that there is no benefit to writing more than
> one block at a time with ODSYNC. And even at half a meg per write,
> DSYNC is slower than ODSYNC with 8K per write! Note the fairly high
> system-time consumption for DSYNC, too. I think this is not so much
> a matter of a really good ODSYNC implementation, as a really bad DSYNC
> one ...

So seems we can use O_DSYNC without losing log write performance
comparing with write() + fsync. Though, we didn't tested write() +
fdatasync()
yet...

Vadim

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