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From: Jürgen Purtz <juergen@purtz.de>
To: pgsql-sql@postgresql.org
Subject: Replication
Date: Wed, 3 Feb 2016 19:46:27 +0100
Message-ID: <56B24B03.4090401@purtz.de> (raw)
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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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