Re: Standby servers and incrementally updated backups

On Friday 29 June 2007 13:47, Erik Jones wrote:
> On Jun 29, 2007, at 10:15 AM, Jim Nasby wrote:
> > On Jun 25, 2007, at 4:54 PM, Erik Jones wrote:
> >> On Jun 25, 2007, at 4:40 PM, Simon Riggs wrote:
> >>> On Mon, 2007-06-25 at 16:00 -0500, Erik Jones wrote:
> >>>> On Jun 25, 2007, at 3:40 PM, Simon Riggs wrote:
> >>>>>> If I'm correct, then for large databases wherein it can
> >>>>>> take hours to take a base backup, is there anything to be
> >>>>>> gained by
> >>>>>> using incrementally updated backups?
> >>>>>
> >>>>> If you are certain there are parts of the database not touched
> >>>>> at all
> >>>>> between backups. The only real way to be sure is to take file
> >>>>> level
> >>>>> checksums, or you can trust file dates. Many backup solutions
> >>>>> can do
> >>>>> this for you.
> >>>>
> >>>> Wait, um, what? I'm still not clear on why you would want to run a
> >>>> backup of an already caught up standby server.
> >>>
> >>> Sorry, misread your question.
> >>>
> >>> While you are running a warm standby config, you will still want
> >>> to take
> >>> regular backups for recoverability and DR. These are additional
> >>> backups,
> >>> i.e they are not required to maintain the warm standby.
> >>>
> >>> You can backup the Primary, or you can backup the Standby, so most
> >>> people will choose to backup the Standby to reduce the overhead
> >>> on the
> >>> Primary.
> >>
> >> Ok, yeah, that's what I was thinking and is where we are headed in
> >> the next month or so here at work: we already have a standby
> >> running and will be adding a second standby server that we will be
> >> using for snapshot backups (packaged with the pertinent wal
> >> files...) as well as periodically bringing the second standby up
> >> to run dumps from just to cover all of our bases and also to be
> >> able to take our main primary server down for maintenance and
> >> still have both a production and standby running. I guess I was
> >> really just wanting to make sure I wasn't missing some other big
> >> usage for incremental backups from the standby.
> >
> > Note that (currently) once you bring a standby up you can't go back
> > to standby mode without restoring the filesystem level backup you
> > started with and replaying everything.
>
> Right, got that.

Which is one reason to keep doing incremental backups, so you can discard, or
at least trim, the number of wal log archives you need to keep around.

On a side note, I think we've found a way around this problem, I'll post a
note once I test it a little more.

--
Robert Treat
Build A Brighter LAMP :: Linux Apache {middleware} PostgreSQL