From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Synchronization levels in SR |
Date: | 2010-05-26 22:00:41 |
Message-ID: | 1274911241.6203.3614.camel@ebony |
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Lists: | pgsql-hackers |
On Wed, 2010-05-26 at 17:31 -0400, Jan Wieck wrote:
> You can do this only with per standby options, by giving each standby a
> weight, or a number of votes. Your DEV server would have a weight of
> zero, while your production standby's have higher weights, depending on
> their importance for your overall infrastructure. As long as majority
> means >50% of all votes in the house, you don't have a split brain risk.
Yes, you could do that with per-standby options.
If you give each standby a weight then the parameter has much less
meaning for the user. It doesn't mean number of replicas any more, it
means something else with local and changeable meaning. A fractional
quorum suffers the same way.
What would make some sense would be to have an option for "vote=0|1" so
that a standby would never take part in the transaction sync when
vote=0.
But you still have the problem of specifying rules if insufficient
servers with vote=1 are available. The reaction to that is to supply
more servers with vote=1, though then you need a way to specify how many
servers with vote=1 you care about.
--
Simon Riggs www.2ndQuadrant.com
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