Re: WAL and commit_delay

From: Larry Rosenman <ler(at)lerctr(dot)org>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, vadim4o(at)email(dot)com
Subject: Re: WAL and commit_delay
Date: 2001-02-17 20:48:13
Message-ID: 20010217144813.B2135@lerami.lerctr.org
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* Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> [010217 14:46]:
> > Right now the WAL preallocation code (XLogFileInit) is not good enough
> > because it does lseek to the 16MB position and then writes 1 byte there.
> > On an implementation that supports holes in files (which is most Unixen)
> > that doesn't cause physical allocation of the intervening space. We'd
> > have to actually write zeroes into all 16MB to ensure the space is
> > allocated ... but that's just a couple more lines of code.
>
> Are OS's smart enough to not allocate zero-written blocks? Do we need
> to write non-zeros?
I don't believe so. writing Zeros is valid.
>
> --
> Bruce Momjian | http://candle.pha.pa.us
> pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 972-414-9812 E-Mail: ler(at)lerctr(dot)org
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