Message-ID: <41177CBE.7070803@Yahoo.com>
Date: Mon, 09 Aug 2004 09:31:42 -0400
From: Jan Wieck <JanWieck@Yahoo.com>
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To: "Joshua D. Drake" <jd@commandprompt.com>
Cc: schen@graciousstyle.com, pgsql-general@postgresql.org
Subject: Re: replication
References: <4113BB1C.9020106@graciousstyle.com>
	<4113C627.9030205@commandprompt.com>
In-Reply-To: <4113C627.9030205@commandprompt.com>
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On 8/6/2004 1:55 PM, Joshua D. Drake wrote:
> Hello,
> 
> The two main replication products available are:
> 
> Slony-I and Mammoth Replicator.
> 
> Slony-I: Open Source, trigger based, batch replication.
> 
> Mammoth Replicator: Closed Source (source license available), integrated 
> (no triggers), live and batch replication.

Out of curiosity, what is the difference between live and batch 
replication?

Slony-I has shown recently that it can achieve replication lags down to 
a second average, with sporadic spikes up to several seconds on packet 
loss in a WAN setup. That was replicating to a virtual machine running 
on a notebook and the DB connections ssh-tunneled over two wireless 
links and the internet ... not exactly what one would call a production 
grade network connection. The server was running a TPC-W ordering mix at 
that time, processing about 60,000 transactions per hour resulting in 
15,000 row updates per hour (the PHP session data was DB-based and 
replicated too). A 10 hour fallback of the replica (the slave system was 
moved from Philadelphia to Toronto and back a weekend later :-) ) was 
cought up in 3 hours against the continuously running main server over 
the WAN, and in about 1.5 hours back in the WLan.

> 
> They are both good solutions (I work for the creators of Mammoth 
> Replicator) that serve different purposes.

Right (and I am the initial creator of Slony-I). Slony-I as a pure 
trigger based approach for example does not aim at fully automatic DDL 
replication.


Jan

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