Re: Warm Standby Setup Documentation

On Fri, Mar 26, 2010 at 01:35:43PM -0500, Ogden wrote:
> On Mar 26, 2010, at 1:32 PM, Greg Smith wrote:
>
> > Bryan Murphy wrote:
> >> The one thing you should be aware of is that when you fail over, your spare has no spares.  I have not found a way
aroundthis problem yet.  So, when you fail over, there is a window where you have no backups while you're building the
newspares.  This can be pretty nerve wracking if your database is like ours and it takes 3-6 hours to bring a new spare
onlinefrom scratch. 
> >
> > If there's another server around, you can have your archive_command on the master ship to two systems, then use the
secondone as a way to jump-start this whole process.  After fail-over, just start shipping from the new primary to that
3rdserver, now the replacement standby, and sync any files it doesn't have.  Then switch it into recovery.  Much faster
thandoing a new base backup from the standby on larger systems. 
>
> How is it possible to use the archive_command to ship to different ones?
>
> archive_command = 'rsync -a %p postgres@192.168.x.x:/usr/local/pgsql/walfiles/%f </dev/null'
> archive_timeout = 120         # force a logfile segment switch after this
>
> I suppose you can put multiple commands there then?

You can always wrap as many commands as you like in a script.
However, there is a pitfall to watch out for when shipping WALs to
multiple standby servers.  Namely your script has to handle failures
of individual WAL shipping targets so that a single target going down
doesn't disrupt operation of the whole cluster.  Please see
http://archives.postgresql.org/pgsql-general/2009-10/msg00590.php
for discussion.

Yar