Re: Problem with Streaming Replication

Hi Kerem,
Thanks to your answer. I think that the correct way is:

1) The master write in her hard drive the WAL files.

2) After this in some moment(asynchronous method), the slave node connect in the shared folder(master) and copy to it all the WAL files.

3) After the slave execute the copy, this execute the instructions inside the WAL files to her database.

My doubt is if the master hd is dead after write some transactions in her WAL before the (2) step happen. In this case i think that the data goig to be lost. And i would like to know if there is a mode of 'force' replicate the WAL file to the slave using some command.

Abraão

>Subject: Re: [ADMIN] Problem with Streaming Replication
> From: blokdiyagram(at)gmail(dot)com
> To: abraao895(at)hotmail(dot)com
> CC: pgsql-admin(at)postgresql(dot)org
> Date: Thu, 30 Jun 2011 15:50:03 +0300
>
> On Thu, 2011-06-30 at 05:21 -0700, abraao895 wrote:
> > Hi,
> >
> > I have a doubt about the WAL-based replication. Suppose this situation:
> >
> > - The PC1(master) write the WAL file in the shared folder in her HD.
> >
> > - The HD of the PC1(master) dead. The WAL file don't have replicated because
> > it is a asynchronous proccess and suppose that this already didn't have
> > happened.
> This is unlikely to happen when you share the folder of the slave server
> to the master as the WAL backup folder.
> >
> > - The PC2(slave) doesn't have the last record.
> Streaming replication occurs on transaction basis. As taken form the
> documentation on
> http://www.postgresql.org/docs/9.0/static/warm-standby.html
>
> "Streaming replication allows a standby server to stay more up-to-date
> than is possible with file-based log shipping. The standby connects to
> the primary, which streams WAL records to the standby as they're
> generated, without waiting for the WAL file to be filled. "
>
> So as soon as it is written on WAL on the master server it is written
> also on the slave node. The shared WAL folder is there in case the slave
> cannot keep up with the master server. Usually on such a situation it
> should not use immediately the WAL logs to keep up. If it happens to use
> wal at a particular time, it is on the disk of the slave server anyway.
>
>