Re: Online base backup from the hot-standby

On 11-06-14 02:52 AM, Jun Ishiduka wrote:
>> I still think that's headed in the wrong direction.
>> (http://archives.postgresql.org/pgsql-hackers/2011-05/msg01405.php)
> Please check these mails, and teach the reason for content of the wrong
> direction.
> (http://archives.postgresql.org/pgsql-hackers/2011-06/msg00209.php)
> (http://archives.postgresql.org/pgsql-hackers/2011-05/msg01566.php)
>
>

Jun, I've been reviewing these threads as a start to reviewing your
patch (I haven't yet looked at the patch).

I *think* the concern is that

1) Today you can do a backup by just calling pg_start_backup('x'); copy
the data directory and
pg_stop_backup(); You do not need to use pg_basebackup to create a
backup. The solution you are proposing would require pg_basebackup to be
used to build backups from standby servers.

2) If I run pg_basebackup but do not specify '-x' then no pg_xlog
segments are included in the output. The relevant pg_xlog segments are
in the archive from the master. I can see situations where you are
already copying the archive to the remote site that the new standby will
be created in so you don't want to have to copy the pg_xlog segments
twice over your network.

What Heikki is proposing will work both when you aren't using
pg_basebackup (as long the output of pg_stop_backup() is somehow
captured in a way that it can be read) and will also work with
pg_basebackup when '-x' isn't specified.

Steve

> --------------------------------------------
> Jun Ishizuka
> NTT Software Corporation
> TEL：045-317-7018
> E-Mail: ishizuka(dot)jun(at)po(dot)ntts(dot)co(dot)jp
> --------------------------------------------
>
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