Re: Best Practice

From: Craig Hagan <hagan_at_cih.com>
Date: Thu, 19 Jan 2012 09:40:27 -0500
Message-ID: <CAFk4TtUj5Heo9ZWW5=Docr5yD4Yw+zpnmke37FUo5Y9csq2o+w_at_mail.gmail.com>



On Thu, Jan 19, 2012 at 9:26 AM, <Laimutis.Nedzinskas_at_seb.lt> wrote:
> >Marcin Przepiorowski <pioro1_at_gmail.com>
> >It makes sens - if you use FSFO and primary database will loose
> connection to standby database and to observer it will shutdown
> automatically preventing environment from split brain when primary DC
> will be available again.
>
> ok, FSFO takes care of split brain. A standard "shoot yourself into your
> head" method is used.
>

correct.

>
>
> >Is is possible to run observer in same place where are your end users
> ? It that case observer will see exactly same situation
> like your users.
>
> Oracle is telling you "The observer should be installed and run on a
> computer system that is separate from the primary and standby systems "
>
> The only question is from which point to observe both databases.
> IMHO, a natural answer: from your most important point. Take your most
> important functionality (e.g. authentication services) and make sure that
> observer detects when primary becomes unavailable to authentication
> purposes.
>
>

an additional answer which is often better is a site which contains neither your primary nor your standby. This would allow a complete datacenter failure to (if synchronized) allow for a failover to occur. Your risk is that
the datacenter/network/rack containing your primary + observer fails, which will prevent your standby from
taking over since the observer will not be able to contact it.

link between DS's was broken. And well, that is VERY correct - if standby
> is accessible then let the primary shoot itself down and use standby.
>

correct, however this can only occur if the observer isn't also isolated from the standby.

One "good" thing is that the observer usually can abide a degree of latency and slowish links, which could allow
you to locate it somewhere a bit further away (e.g. someone's cloud, etc).

  • craig
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Received on Thu Jan 19 2012 - 08:40:27 CST

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