Re: WAL and commit_delay - Mailing list pgsql-hackers

From Larry Rosenman
Subject Re: WAL and commit_delay
Date
Msg-id 20010217144813.B2135@lerami.lerctr.org
Whole thread Raw
In response to Re: WAL and commit_delay  (Bruce Momjian <pgman@candle.pha.pa.us>)
Responses Re: WAL and commit_delay  (Bruce Momjian <pgman@candle.pha.pa.us>)
List pgsql-hackers
* Bruce Momjian <pgman@candle.pha.pa.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@candle.pha.pa.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@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749


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