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Re: Re: Backup and Recovery

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Re: Backup and Recovery
Date: 2001-07-04 15:04:13
Message-ID: 200107041504.f64F4DZ05568@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
> > All that is missing is a program, that can take a consistent physical
> > snapshot (as it was after a particular checkpoint) and would replay
> > the WAL after a restore of such a snapshot. This replay after a
> > consistent snapshot is probably as simple as making the WAL files
> > available to the standard startup rollforward (redo) mechanism, that
> > is already implemented.
> 
> How would you take a physical snapshot without interrupting database 
> operation?  Is a physical/binary snapshot a desirable backup format?  
> People seem to want to be able to restore from ASCII dumps.
> 
> Also, isn't the WAL format rather bulky to archive hours and hours of?
> I would expect high-level transaction redo records to be much more compact;
> mixed into the WAL, such records shouldn't make the WAL grow much faster.

The page images are not needed and can be thrown away once the page is
completely sync'ed to disk or a checkpoint happens.  

The row images aren't that large.  I think any solution would have to
handle page images and row images differently.


-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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