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Re: Failover of the Primary database and starting the standby database in Postgresql in PITR configuraiton?

From: "libra dba" <libra(dot)dba(at)gmail(dot)com>
To: salman <salmanb(at)quietcaresystems(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Failover of the Primary database and starting the standby database in Postgresql in PITR configuraiton?
Date: 2008-02-28 14:36:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-admin
Hey Salman,

Thanks a lot for  all your guidance and help. It has really been a great
help. I appreciate your quick replies.

Which replication in postgres is better  ?
SLONY or WARM STANDBY (usning wal).

Another thing which haunts me is that, if we have a warm standby, the
recovery process on the standby server reads an archived file only if it is
16MB, if it is small, the standby server goes down as shown

*quote from the logfile on standby*
*FATAL:  archive file "000000010000000100000032" has wrong size: 491520
instead of 16777216
LOG:  startup process (PID 13177) exited with exit code 1
LOG:  aborting startup due to startup process failure
LOG:  database system was interrupted while in recovery at log time
2008-02-28 00:47:39 EST
Usually, an archive file is written every minute. Now, if the last archive
was written at 12:05:00, and the primary server goes down at 12:05:37, the
archive is not generated for the last 37 seconds. The archive file which was
written at 12:05:00 would be applied to the standby. But what will happen to
transactions which happen in the last 37 seconds before the crash???

Do we loose that data???


On Wed, Feb 27, 2008 at 4:05 PM, salman <salmanb(at)quietcaresystems(dot)com>

> libra dba wrote:
> > continuing with the postgres replication using WARM STANDBY, what
> happens to
> > the wal_files which keeps on generating on the primary?
> >
> > Do we have to manually remove them or they are removed automatically,
> once
> > they have been recovered on the warm standby?
> >
> > Also a quick question, do we have to have a NFS for the wal_files, which
> > will be mounted on both the servers, or we can have folders on each
> server
> > and configure DRBD between them, so that whatever happens on one is
> copied
> > automatically on to the other.
> >
> > Thanks!
> >
> This is what I use -- may not be the best approach, but it has worked
> quite well for me so far:
> archive_command = 'gzip %p; rsync -av %p.gz -e \"ssh -p portNum -i
> /home/postgres/.ssh/id_dsa\"
> postgres(at)rhostname:/usr/local/postgresql/archives/recovery/%f.gz && rm
> -f %p.gz'

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