Horton

Re: initdb and fsync

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew@dunslane.net>
Date: 2012-03-14T04:23:03Z
Lists: pgsql-hackers

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On Tue, 2012-03-13 at 09:42 +0100, Andres Freund wrote:
> for recursively everything in dir:
>    posix_fadvise(fd, POSIX_FADV_DONTNEED);
> 
> for recursively everything in dir:
>    fsync(fd);

Wow, that made a huge difference!

  no sync:      ~ 1.0s
  sync:         ~10.0s
  fadvise+sync: ~ 1.3s

Patch attached.

Now I feel much better about it. Most people will either have fadvise, a
write cache (rightly or wrongly), or actually need the sync. Those that
have none of those can use -N.

Regards,
	Jeff Davis