Re: Shared WAL archive between master and standby: WALs not always identical

On 02/27/2017 04:40 PM, Sasa Vilic wrote:
> Hallo,
>
> I am trying to setup shared WAL archive between master and standby.
> Standby is synchronously streaming from master and both servers run with
> archive_mode = always. The ideas is that when promoting standby to
> master we would not missed WALs.

I seem to be missing the point of duplicating your effort.

You are doing this, correct?:

Master WAL --> WAL archive <--
|
Master stream --> Standby --> |

I can't see how the Standby contributes anything to the archive that it
does not already have from the Master?

>
> My problem is that sometimes WAL uploaded from master and from slave are
> not 100% identical. In most cases they are but occasionally they are
> not. I have written small script that ensures that upload is free of
> race condition and I log md5 sum of each WAL. Aren't WALs from master
> and standby supposed to be identical? After all, standby is just
> consuming WAL that it is receiving from master ...
>
> Or do you have any better suggestion on how to achieve continuous
> incremental backup?
>
> Thanks in advance

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com