From: =?UTF-8?Q?J=c3=bcrgen_Purtz?= <juergen@purtz.de>
Subject: Replication
To: pgsql-sql@postgresql.org
Message-ID: <56B24B03.4090401@purtz.de>
Date: Wed, 3 Feb 2016 19:46:27 +0100
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Hi all,

replication is a complex topic, so I tried to get a systematic view on 
it. Among others I found 4 mutually independent (?) concepts:

  * Log-Shipping vs. Streaming (LS vs. S)
  * Physical Format vs. Logical Decoded Format (PFo vs. LFo)
  * Synchronous vs. asynchronous transfer (STr vs ASTr)
  * hot standby vs. warm standby

'Mutually independent' implies that there are 2 power 4 = 16 possible 
combinations. But I believe, there are some limitations.

First, hot and warm standby (at the standby site) are possible in all 
cases. Second, for me the following 5 out of 8 seems to be possible:

LS - PFo - ASTr  (Asynchronous Log-shipping in Physical Format)
S - PFo - STr      (Synchronous Streaming in Physical Format)
S - PFo - ASTr  (Asynchronous Streaming in Physical Format)
S - LFo - STr    (Synchronous Streaming in Logical Format)
S - LFo - ASTr  (Asynchronous Streaming in Logical Format)

My questions are:

 1. Do you agree to this systematization into 4 categories?
 2. Do you agree, that only this 5 out of 8 possibilities exist?

Regards
Jürgen Purtz


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    Hi all,<br>
    <br>
    replication is a complex topic, so I tried to get a systematic view
    on it. Among others I found 4 mutually independent (?) concepts:<br>
    <ul>
      <li>Log-Shipping vs. Streaming (LS vs. S)<br>
      </li>
      <li>Physical Format vs. Logical Decoded Format (PFo vs. LFo)<br>
      </li>
      <li>Synchronous vs. asynchronous transfer (STr vs ASTr)<br>
      </li>
      <li>hot standby vs. warm standby<br>
      </li>
    </ul>
    'Mutually independent' implies that there are 2 power 4 = 16
    possible combinations. But I believe, there are some limitations. <br>
    <br>
    First, hot and warm standby (at the standby site) are possible in
    all cases. Second, for me the following 5 out of 8 seems to be
    possible:<br>
    <br>
    LS - PFo - ASTr  (Asynchronous Log-shipping in Physical Format)<br>
    S - PFo - STr      (Synchronous Streaming in Physical Format)<br>
    S - PFo - ASTr  (Asynchronous Streaming in Physical Format)<br>
    S - LFo - STr    (Synchronous Streaming in Logical Format)<br>
    S - LFo - ASTr  (Asynchronous Streaming in Logical Format)<br>
    <br>
    My questions are:<br>
    <ol>
      <li>Do you agree to this systematization into 4 categories?</li>
      <li>Do you agree, that only this 5 out of 8 possibilities exist?</li>
    </ol>
    <p>Regards<br>
      Jürgen Purtz<br>
      <br>
    </p>
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