Re: RAC with one node as a DR solution
- From: Chris King <ckaj111@xxxxxxxx>
- To: "Ruel, Chris" <Chris.Ruel@xxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 4 Mar 2014 08:56:15 -0800 (PST)
Thanks, Chris, for that excellent and thorough run down!
First let me say, the only reason we're looking at the three node option I
described is that our company can get a 3rd node cheaper than active data
guard, because of our corporate agreements with oracle.
I really liked your idea of running two standby databases, keeping one in read
only and refreshing it daily.. Can I assume there's no extra cost to run the
second standby on the same DR server if you're licencing by processor? If so,
this could be the ticket for us. Thanks again.
On Tuesday, March 4, 2014 11:32:58 AM, "Ruel, Chris" <Chris.Ruel@xxxxxxx> wrote:
I am not 100% sure I follow what you are trying to describe and also my
definitions of DR may differ from you or others. In any case, here is my take:
1. RAC is not a DR solution. I would categorize RAC as an HA (High
Availability) solution. RAC protects you from node/isolated hardware failures
with respect to HA.
2. Solutions for DR from Oracle would certainly include Dataguard and
some would even include Streams/Replication and GoldenGate.
3. A DR solution implies that you have a separate system that is isolated
(geographically separate) from the primary site to insulate from things like
localized power outages, server room fire, or even a natural disaster that
takes out a data center.
4. While there is such thing as extended RAC (long distance nodes
connected by dark fiber) you probably don’t want to even consider that if cost
is a concern of yours.
You know, if you are simply looking for a DR solution, I think Dataguard is
probably your best bet. You do not have to pay for Active DataGuard (AD) to
use regular Dataguard. However, Regular Dataguard requires that you license
your remote site which can be expensive by itself...especially when you
consider that w/o AD its usage is limited.
FWIW, one of the things I configured in the past used non-Active Dataguard.
The client wanted to use the remote site for some things though. W/o AD, the
only option really is to open the database read only to use it. When that
occurs, of course, you fall behind keeping it up with the primary. Instead, we
created two standby database on the remote server. One, we left in apply mode
all the time for failover purposes. The other was opened (read/write) every
morning at 8:00...used all day, then, closed at 8:00 PM, flashed back so
archives could be applied from the primary and brought back up to speed so that
when it opened at 8:00 AM the next day it was a fresh copy of the primary.
Now, your business rules and needs may not support this sort of configuration
but it was one way we were able to leverage our standby site for some usage
while still staying protected and minimizing costs.
Another option for DR outside of Oracle is to use some sort of wide-area san
mirroring...then, you could have Oracle installed at the remote site such that
all you need to do is shutdown the primary and start it remotely. I think
though that there is a lot of gray area in terms of licensing this
configuration as you would probably want to periodically test it which would
require starting the software stack. With RAC One Node, from my understanding,
you have 10 calendar days per year that you can “activate” your secondary node
without a licensing penalty (for things like maintenance, patches, etc.).
Perhaps, you could use SAN mirroring with RAC One Node and avoid the cost of
licensing your DR site. If a failure is detected on the primary node, The
secondary node would start up. Personally, I have zero experience with a
wide-area RAC One Node configuration...I am just theorizing a possible solution
for you that might be worth looking into.
Good luck!
Chris..
Chris Ruel * Oracle Database Administrator
cruel@xxxxxxx* Desk:317.759.2172 * Cell 317.523.8482
From:oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Chris King
Sent: Tuesday, March 04, 2014 10:45 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: RAC with one node as a DR solution
I'm considering a two-node RAC for a new production environment. For the DR,
I'd hoped to use active data guard, but it's very expensive. I've avoided the
architectural option of adding a third node, but locating it in the DR
environment, because the network to DR will be slower.
Is there a way to set up 3-node RAC, with one node as DR, such that the node in
DR can be set to NOT hold up the other two nodes due to any network latency?
The node in DR would not have to be up to the minute. It would be acceptable to
be up to 30 minutes behind.
Thanks in advance for your feedback!
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