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help / color / mirror / Atom feedFrom: Bruce Momjian <[email protected]>
To: Simon Riggs <[email protected]>
Cc: Thomas F. O'Connell <[email protected]>
Cc: [email protected]
Subject: Re: [DOCS] Incrementally Updated Backups: Docs Clarification
Date: Thu, 6 Mar 2008 20:46:58 -0500 (EST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
I have updated the docs by changing a few words, patch attached.
---------------------------------------------------------------------------
Simon Riggs wrote:
> On Thu, 2007-04-19 at 15:48 -0500, Thomas F. O'Connell wrote:
>
> > "If we take a backup of the standby server's files while it is
> > following logs shipped from the primary, we will be able to reload
> > that data and restart the standby's recovery process from the last
> > restart point. We no longer need to keep WAL files from before the
> > restart point. If we need to recover, it will be faster to recover
> > from the incrementally updated backup than from the original base
> > backup."
> >
> >
> > I'm specifically confused about the meaning of the following phrases:
> >
> >
> > "backup of the standby server's files" - Which files?
>
> the files that make up the database server:
> - data directory
> - all tablespace directories
>
> > "reload that data" - What does this mean in postgres terms?
>
> copy back from wherever you put them in the first place
>
> "that data" referring to the "files that make up the db server"
>
> > "last restart point" - What is this? Wouldn't it be able to restart
> > from the last recovered file, which would presumably occur later than
> > the last restart point?
>
> No, we don't restart file-by-file.
>
> http://developer.postgresql.org/pgdocs/postgres/continuous-archiving.html#BACKUP-PITR-RECOVERY
>
> "If recovery finds a corruption in the WAL..." onwards explains the
> restart mechanism. It's much like checkpointing, so we don't restart
> from the last log file we restart from a point possibly many log files
> in the past.
>
> > Does this mean make a filesystem backup of the standby server's data
> > directory while it's stopped, and then start it again with that data
> > and the restricted set of WAL files needed to continue recovery?
>
> No need to stop server. Where do you read you need to do that?
>
> > I'd like to see the language here converted to words that have more
> > meaning in the context of postgres. I'd be happy to attempt a revision
> > of this section once I'm able to complete an incrementally updated
> > backup successfully.
>
> Feel free to provide updates that make it clearer.
>
> > Here's how I envision it playing out in practice:
> >
> >
> > 1. stop standby postgres server
> > 2. [optional] preserve data directory, remove unnecessary WAL files
> > 3. restart standby server
>
> step 2 only.
>
> Clearly not an optional step, since its a 1 stage process. :-)
>
> --
> Simon Riggs
> EnterpriseDB http://www.enterprisedb.com
>
>
>
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>
> http://www.postgresql.org/docs/faq
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Attachments:
[text/x-diff] /rtmp/diff (1.0K, 2-%2Frtmp%2Fdiff)
download | inline diff:
Index: doc/src/sgml/backup.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/backup.sgml,v
retrieving revision 2.114
diff -c -c -r2.114 backup.sgml
*** doc/src/sgml/backup.sgml 13 Feb 2008 22:44:06 -0000 2.114
--- doc/src/sgml/backup.sgml 7 Mar 2008 01:40:26 -0000
***************
*** 1814,1820 ****
</para>
<para>
! If we take a backup of the standby server's files while it is following
logs shipped from the primary, we will be able to reload that data and
restart the standby's recovery process from the last restart point.
We no longer need to keep WAL files from before the restart point.
--- 1814,1820 ----
</para>
<para>
! If we take a backup of the standby server's data directory while it is processing
logs shipped from the primary, we will be able to reload that data and
restart the standby's recovery process from the last restart point.
We no longer need to keep WAL files from before the restart point.
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