Subject: Re: Testing hot standby on same server sharing same
 tablespace directory
To: Sreekanth Palluru <Sreekanth.Palluru@superchoice.com.au>,
 "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
References: 
 <4CCCD44C0EB1284FA34A4FDD88B7E4E8E64654@abel.nb.superchoice.com.au>
From: Ian Barwick <ian@2ndquadrant.com>
Message-ID: <57216D8E.2080907@2ndquadrant.com>
Date: Thu, 28 Apr 2016 10:55:26 +0900
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On 04/28/2016 08:45 AM, Sreekanth Palluru wrote:
> 
> Hi
> 
> I am testing hot standby on same server (version 9.5.2) , everything works well. 
> I have a doubt regarding sharing of tablespace directory by these two databases .
>
> I have created a tablespace and moved few objects and I happen to see that same
> directory was being used by standby node aka slave node and to my surprise it still works
> without any issues.
> 
> Is this expected ? 

Both instances will start and initially appear to function, but you are guaranteed
to run into unexpected behaviour and some kind of corruption.

Try e.g. creating and populating a table, then pausing replay on the standby; then
drop and recreate/repopulate the same table.

> I was expecting some sort of warnings from Postgres or am I missing something

No, there's nothing which could warn about this particular scenario.


Regards

Ian Barwick


-- 
 Ian Barwick                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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