Re: increasing the default WAL segment size

On 26/08/16 05:43, Josh Berkus wrote:
> On 08/25/2016 01:12 PM, Robert Haas wrote:
>>> I agree that #4 is best. I'm not sure it's worth the cost. I'm not worried
>>>> at all about the risk of master/slave sync thing, per previous statement.
>>>> But if it does have performance implications, per Andres suggestion, then
>>>> making it configurable at initdb time probably comes with a cost that's not
>>>> worth paying.
>> At this point it's hard to judge, because we don't have any idea what
>> the cost might be.  I guess if we want to pursue this approach,
>> somebody will have to code it up and benchmark it.  But what I'm
>> inclined to do for starters is put together a patch to go from 16MB ->
>> 64MB.  Committing that early this cycle will give us time to
>> reconsider if that turns out to be painful for reasons we haven't
>> thought of yet.  And give tool authors time to make adjustments, if
>> any are needed.
> The one thing I'd be worried about with the increase in size is folks
> using PostgreSQL for very small databases.  If your database is only
> 30MB or so in size, the increase in size of the WAL will be pretty
> significant (+144MB for the base 3 WAL segments).  I'm not sure this is
> a real problem which users will notice (in today's scales, 144MB ain't
> much), but if it turns out to be, it would be nice to have a way to
> switch it back *just for them* without recompiling.
>
Let such folk use Microsoft Access???  <Ducks & runs away very fast!>


More seriously:
Surely most such people would be using very old hardware & not likely to 
be upgrading to the most recent version of pg in the near future?  And 
for the ones using modern hardware: either they have enough resources 
not to notice, or very probably will know enough to hunt round for a way 
to reduce the WAL size - I strongly suspect.

Currently, I'm not support pg in any production environment, and using 
it for testing & keeping up-to-date with pg.  So it would affect me - 
however, I have enough resources so it is no problem in practice.



Cheers,
Gavin