Обсуждение: Question about multiple slaves and Master loss.

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

> -----Original Message-----
> From: Evan Rempel [mailto:erempel@uvic.ca]
> Sent: Wednesday, December 07, 2011 1:12 PM
> To: Nicholson, Brad (Toronto, ON, CA)
> Cc: Chris Hoover; pgsql-admin@postgresql.org Admin
> Subject: Re: [ADMIN] Question about multiple slaves and Master loss.
>
> 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.
>

That's called cascaded replication.  It's not currently supported, but coming in 9.2 I believe.

Brad.