Re: Best Practice
- From: Laimutis.Nedzinskas@xxxxxx
- To: pioro1@xxxxxxxxx
- Date: Thu, 19 Jan 2012 16:26:48 +0200
>Marcin Przepiorowski <pioro1@xxxxxxxxx>
>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.
>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.
You need to draw the whole diagram: end user -> network -> load balancer ->
network -> app servers -> database.
An interesting point is that observer MAY NEED to failover a primary
database which is completely healthy just like in our case when network
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.
Brgds, Laimis N
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From: Marcin Przepiorowski <pioro1@xxxxxxxxx>
To: Laimutis.Nedzinskas@xxxxxx
Cc: ORACLE-L <oracle-l@xxxxxxxxxxxxx>
Date: 2012.01.19 13:11
Subject: Re: Best Practice
On Thu, Jan 19, 2012 at 10:08 AM, <Laimutis.Nedzinskas@xxxxxx> wrote:
> We had an interesting case: a network failure between our DC's (data
> centers - one is used as primary and the other as standby as far as
> databases are concerned)
>
>
> In our case observer runs on standby DC. It decided to failover of
course.
> The decision happened to be the correct one at least from admins point of
> view: the failover DC was still accessible to us, we could connect and
> restart what failed to failover, etc. End users could connect too.
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.
>
> You see: you need to consider what end customer functionality needs HA
most
> and start from that. What's the purpose to have a failover if the DC is
not
> accesible to the end users?
>
> If only isolated db/db server failure is concerned then you can run your
> observer on just a standby server. It will do the job: primary goes down,
> observer is running on standby, standby fails ower.
>
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.
regards,
--
Marcin Przepiorowski
http://oracleprof.blogspot.com
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