Re: 9.6 and fsync=off

On Thursday, April 28, 2016, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> On 27 April 2016 at 17:04, Craig Ringer <craig(at)2ndquadrant(dot)com
> <javascript:_e(%7B%7D,'cvml','craig(at)2ndquadrant(dot)com');>> wrote:
>
>> On 27 April 2016 at 21:44, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
>> <javascript:_e(%7B%7D,'cvml','tgl(at)sss(dot)pgh(dot)pa(dot)us');>> wrote:
>>
>>> Petr Jelinek <petr(at)2ndquadrant(dot)com
>>> <javascript:_e(%7B%7D,'cvml','petr(at)2ndquadrant(dot)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.

David J.