Re: RAC Vs Standby Database between Primary and Secondary Data Centers
- From: Dan Norris <dannorris@xxxxxxxxxxxxx>
- To: richard.goulet@xxxxxxxxxxxxx, mssql_2002@xxxxxxxxx, oracle-l@xxxxxxxxxxxxx
- Date: Mon, 21 Jan 2008 09:53:00 -0800 (PST)
Dick,
Here's where I think we need to make clear what defines "high availability"
versus what becomes "disaster recovery". Many sites want/need both. In my
dictionary, I define high availability as a system that can tolerate a failure
of a single component without affecting the application availability. There's
also "fault tolerance", but that starts to get into a whole other world, so
let's put that out of scope for now. Disaster recovery in my book is defined as
a system that can handle failure of a data center or geographic location
without affecting application availability. I acknowledge that many if not most
disaster recovery solutions do have some outage associated with their failover,
but that outage is generally shorter than the time required to restore/recover
the primary site at an alternate location.
Having said that, I don't disagree with your comments, but felt the need to
point out that high availability does not necessarily equal disaster recovery.
Also, I submit that RAC is not primarily designed as a disaster recovery
solution. As another poster mentioned, RAC does have some support for "stretch
clusters", but they are not widely used and the MAA still recommends standby
database in combination with RAC (at least the last time I read it).
To the OP, I think the MAA has some good ideas if you're looking for
architecture decision points. It is online at
http://www.oracle.com/technology/deploy/availability/htdocs/maa.htm.
Dan
----- Original Message ----
From: "Goulet, Dick" <richard.goulet@xxxxxxxxxxxxx>
To: mssql_2002@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Sent: Monday, January 21, 2008 9:24:26 AM
Subject: RE: RAC Vs Standby Database between Primary and Secondary Data Centers
Bob,
RAC is not a High Availability solution in and of itself. A RAC
system must have all servers in the same physical location which leaves
you vunerable to earth quakes, fires, etc..... Standby database is
there to protect you against these types of disasters by placing an
identical copy of your database in a separate physical location that
presumably will not get hit by the "9/11 factor" at the same time. The
first thing you should do is determine what your trying to protect
against and then plan accordingly. RAC will protect you against a
single server failure in your local data center. Standby can protect
you against a single server failure as well, but adds protection for a
9/11 incident at the same time..
______________________________________________________________
Dick Goulet / Capgemini
North America P&C / East Business Unit
Senior Oracle DBA / Hosting
Office: 508.573.1978 / Mobile: 508.742.5795 / www.capgemini.com
Fax: 508.229.2019 / Email: richard.goulet@xxxxxxxxxxxxx
45 Bartlett St. / Marlborough, MA 01752
Together: the Collaborative Business Experience
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