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Re: Warm standby architecture opinions

From: Jeff Frost <jeff(at)frostconsultingllc(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: sfpug(at)postgresql(dot)org
Subject: Re: Warm standby architecture opinions
Date: 2005-04-19 16:49:27
Message-ID: (view raw, whole thread or download thread mbox)
Lists: sfpug
On Tue, 19 Apr 2005, Josh Berkus wrote:

> Well, what I'm saying is that switching masters on Slony is a couple of 2-line
> commands and can be done with the servers live.   To switch using PITR, you
> pretty much have to shut down one server and restart the other.  So it's a
> question of whether you only expect to be doing this for failures, or more
> frequently for various purposes (upgrades, new feature tests, etc.)

Now I see what you're saying.  So, actually, the more correct answer to your 
question would have been that we forsee using the backup server rarely.

> Dells are crap.   Buy something else.   You'll get 3x the performance for only
> 25% more money.  I'm pretty fond of dual-opteron home-builds, only about
> $2500.  IBM sells some decent Opteron machines these days (so does Sun, but
> they're two expensive, and HP's suffer from bad RAID).   Or, in the 2nd tier,
> both Penguin Computing and Microway have relatively good reputations.

Do you mean 3x the performance for the NAS or 3x the performance for the 
actual server.  3x the performance for 25% extra cost sounds quite impressive, 
though I suspect that's not really the case.  You have of course picqued my 
interest, and we haven't placed the order yet, so let me look into the IBMs 
and Penguins.

> As a comparison:  I have one dot-com client running on Dell 2650s, and they
> have a 3-machine Slony cluster that just keeps up with their load.  I've
> another client with a website about twice as busy, and they run everything
> off of a single quad-Opteron home build.

And their queries are all comparable?

>> 3) It's used for reads and writes on a busy website. I would say it's a bit
>> more read intensive than write intensive, but that could change.  As usual
>> with these things, management wants maximum uptime.
> Well, I'm really seeing Slony in your future.  The reason is upgrades.  Slony
> is the only solution that's going to allow you to upgrade to 8.1 without
> taking the site down.   Admittedly, it will make DDL considerably more
> painful.   So here's my suggestion:
> 1) devise a PITR or shared-storage based solution (btw, the Dell NAS is *not*
> adequately redundant shared storage) for the next 6 months, while your app is
> still being developed.
> 2) when you think the vast majority of tinkering is done, switch to a
> Slony-based solution.  WHo knows, maybe by that time Slony-II will be out.

Thanks for the feedback Josh!

Jeff Frost, Owner 	<jeff(at)frostconsultingllc(dot)com>
Frost Consulting, LLC
Phone: 650-780-7908	FAX: 650-649-1954

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