Re: Configuring synchronous replication

On Thu, 2010-09-23 at 20:42 +0300, Heikki Linnakangas wrote:
> If you want the behavior where the master doesn't acknowledge a
> commit 
> to the client until the standby (or all standbys, or one of them
> etc.) 
> acknowledges it, even if the standby is not currently connected, the 
> master needs to know what standby servers exist. *That's* why 
> synchronous replication needs a list of standby servers in the master.
> 
> If you're willing to downgrade to a mode where commit waits for 
> acknowledgment only from servers that are currently connected, then
> you don't need any new configuration files. 

As I keep pointing out, waiting for an acknowledgement from something
that isn't there might just take a while. The only guarantee that
provides is that you will wait a long time. Is my data more safe? No.

To get zero data loss *and* continuous availability, you need two
standbys offering sync rep and reply-to-first behaviour. You don't need
standby registration to achieve that.

> But that's not what I call synchronous replication, it doesn't give
> you the guarantees that 
> textbook synchronous replication does.

Which textbook?

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 Simon Riggs           www.2ndQuadrant.com
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