Re: 9.6 and fsync=off

On Thursday, April 28, 2016, Simon Riggs <simon@2ndquadrant.com> wrote:

On 27 April 2016 at 17:04, Craig Ringer <craig@2ndquadrant.com> wrote:

On 27 April 2016 at 21:44, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Petr Jelinek <petr@2ndquadrant.com> writes:
> +1 (Abhijit's wording with data loss changed to data corruption)

I'd suggest something like

#fsync = on                             # flush data to disk for crash safety
                                        # (turning this off can cause
                                        # unrecoverable data corruption!)

Looks good.

The docs on fsync are already good, it's just a matter of making people think twice and actually look at them. 

If fsync=off and you turn it on, does it fsync anything at that point?

Or does it mean only that future fsyncs will occur?

http://www.postgresql.org/docs/current/static/runtime-config-wal.html

4th paragraph in the fsync section.