Message-ID: <1411544542.542275de20713@imp.free.fr>
Date: Wed, 24 Sep 2014 09:42:22 +0200
From: gparc@free.fr
To: "Campbell, Lance" <lance@illinois.edu>
Cc: "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
Subject: Re: Clarification on pg_basebackup
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 <B75CD08C73BD3543B97E4EF3964B7D701FBB7279@CITESMBX1.ad.uillinois.edu>
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Selon "Campbell, Lance" <lance@illinois.edu>:

 PostgreSQL 9.3
 Would someone be able to clarify if one should use the -X option with
 pg_basebackup when your intention is to include all WAL files created?  There
 are two scenarios.  The first scenario listed below makes sense using the -X
 option.  Bus scenario #2 has me a little confused.  I don't want to cause any
 issues when restoring.


 1)      Use pg_basebackup for a fully standalone restorable snapshot of the
 database using the -X parameter.  When a failure occurs you restore the
 database to that exact point in time.

 2)      You restore from a pg_basebackup and you also apply all of the WAL
 files since the last pg_basebackup.  Do you want to use the -X option when
 doing the pg_basebackup if your intention is to have all of the WAL files
 since you backed up last?  Or does it matter.  Would PostgreSQL just ignore
 the duplicate WAL files that were created by the -X option during the
 pg_basebackup?

 Thanks for your clarification.  This is a hard scenario to test.

 Thanks,

 Lance Campbell<http://illinois.edu/person/lance>
 Software Architect
 Web Services at Public Affairs
 217-333-0382
 [University of Illinois at Urbana-Champaign logo]<http://illinois.edu/>


For security, I will do both i.e pg_basebackup -X + continuous WAL archiving.
Reason : you never know what could happen with your WAL archiving process.
At least with -X you will have a "restartable" backup.


Regards

Gilles


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