From: Simon Riggs <simon@2ndQuadrant.com>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: greg@2ndquadrant.com
Cc: hannu@2ndquadrant.com
Cc: heikki.linnakangas@enterprisedb.com
Cc: robertmhaas@gmail.com
Cc: stefan@kaltenbrunner.cc
Cc: josh@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: Sync Rep Design
Date: Sun, 02 Jan 2011 17:43:02 +0000
Message-ID: <1293990182.2090.1914.camel@ebony> (raw)
In-Reply-To: <4D205D650200002500038EDC@gw.wicourts.gov>
References: <4D205D650200002500038EDC@gw.wicourts.gov>
On Sun, 2011-01-02 at 11:11 -0600, Kevin Grittner wrote:
> Simon Riggs wrote:
>
> > Do you agree that requiring response from 2 sync standbys, or
> > locking up, gives us 94% server availability, but 99.9992% data
> > durability?
>
> I'm not sure how to answer that. The calculations so far have been
> based around up-time and the probabilities that you have a machine up
> at any moment and whether you can have confidence that if you do, you
> have all committed transactions represented. There's been an implied
> assumption that the down time is unplanned, but not much else. The
> above question seems to me to get into too many implied assumptions
> to feel safe throwing out a number without pinning those down a whole
> lot better. If, for example, that 2% downtime always means the
> machine irretrievably went up in smoke, hitting unavailable means
> things are unrecoverable. That's probably not the best assumption
> (at least outside of a combat zone), but what is?
Not really relevant. There's no room at all for downtime of any kind in
a situation where all servers must be available.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
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To: pgsql-hackers@postgresql.org
Cc: simon@2ndQuadrant.com, Kevin.Grittner@wicourts.gov, greg@2ndquadrant.com, hannu@2ndquadrant.com, heikki.linnakangas@enterprisedb.com, robertmhaas@gmail.com, stefan@kaltenbrunner.cc, josh@postgresql.org
Subject: Re: Sync Rep Design
In-Reply-To: <1293990182.2090.1914.camel@ebony>
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