Message-ID: <4EDFAC67.9040809@uvic.ca>
Date: Wed, 07 Dec 2011 10:11:51 -0800
From: Evan Rempel <erempel@uvic.ca>
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To: "Nicholson, Brad (Toronto, ON, CA)" <bnicholson@hp.com>
CC: Chris Hoover <revoohc@gmail.com>,
	"pgsql-admin@postgresql.org Admin" <pgsql-admin@postgresql.org>
Subject: Re: Question about multiple slaves and Master loss.
References: 
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	<EC55DC235432104F8255702A8D7344D925702255@G9W0741.americas.hpqcorp.net>
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 <EC55DC235432104F8255702A8D7344D925702255@G9W0741.americas.hpqcorp.net>
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Can you have a slave of a slave?

Basically set up

A --> B --> C
also
A --> D --> E

if A goes down, promote B which is protected by C
If B goes down, D is your protection for A
If C goes down, who cares.

It takes 5 machines, but would give great protection.

Evan.


Nicholson, Brad (Toronto, ON, CA) wrote:
> *From:* pgsql-admin-owner@postgresql.org 
> [mailto:pgsql-admin-owner@postgresql.org] *On Behalf Of *Chris Hoover
> *Sent:* Wednesday, December 07, 2011 12:05 PM
> *To:* pgsql-admin@postgresql.org Admin
> *Subject:* [ADMIN] Question about multiple slaves and Master loss.
> 
>  
> 
> I'm pretty sure that the answer to this question is no, but I wanted to 
> verify.
> 
>  
> 
> Given the following scenario (pg 9.0):
> 
>  
> 
> Server A (Master), Server B (A's streaming replication Slave), Server C 
> (A's streaming replication Slave)
> 
>  
> 
> If you lose Server A, is there anyway to promote Server B to master and 
> keep Server C as B's slave without having to rebuild C from a backup of B? 
> 
>  
> 
> Basically, I'd like to be able to have 2 slaves running so that when the 
> master goes down, we can bring one slave online, and still have the 
> ability to very quickly recover if the new master where to fail before 
> server A could be recovered.
> 
>  
> 
> Thanks,
> 
>  
> 
> Chris
> 
>  
> 
> Not that I am aware of.  In practice though, C and B should me more or 
> less equivalent so as long as you are using a differential copy like 
> rsync you should be able to bring C up as a replica of B very quickly.  
> There is of course a small window though where you are not protected.
> 
>  
> 
> Brad.
> 


-- 
Evan Rempel                               erempel@uvic.ca
Senior Systems Administrator                 250.721.7691
Unix Services, University Systems, University of Victoria