Re: Running Oracle RAC 11g and Data Guard across two data centres

From: Bob Jones <email_at_me.not>
Date: Thu, 9 Jul 2009 19:35:21 -0500
Message-ID: <2Uv5m.6371$>

"DG problem" <> wrote in message
> Apologies if this question is too general or not enough information
> given.
> What is the best way to configure a data warehouse and an OLTP system
> (OLTP system would generate about 60Gb of archive logs a day at about
> 150 commits per second) on the following hardware?
> Two separate data centres with a fibre link.
> Each data centre has two boxes (each box has a Sun M4000, 2 x quad
> core 2.4GHz) and 35Tb of storage.
> Running Oracle 11g with RAC and Data Guard.
> The data warehouse would be a copy of the OLTP data and would
> obviously grow as the OLTP database grows. OLTP data would be archived
> to the data warehouse.
> The current proposal is to run RAC across both boxes in one data
> centre. ie, have both databases running on both boxes with RAC and
> then to use data guard for the standbys in the other data centre.
> However, this seems far from optimal to me. Wouldn't it be better to
> run RAC across both data centres?
> Does it make sense to use RAC and data guard together as mentioned
> above?
> If RAC was used across both data centres does this mean that:
> 1) You can achieve 100% uptime even if one data centre shuts down or
> suffers catastrophic failure?
> 2) You can achieve 100% uptime while patching/upgrading one instance
> at a time?
> 3) You woudln't need to use data guard as RAC provides fail over?
> If RAC is only run in one data centre, and that data centre goes down,
> then you will have down time while failing over to the standby
> databases in the other data centre and if you are not running data
> guard in maximum protection (due to possible performance issues caused
> by latency), you could potentially lose data? I realise that with a
> fast high bandwidth connection, data guard will run in maximum
> protection with minimum performance hit, however, politics sometimes
> cuts costs by cutting bandwidth :(
> I realise that there are lots of new features in data guard 11g, eg
> standby databases can be open for queries. Are there any other
> features that could be used?
> Any other tips or criticisms?

Why would you want a RAC across a distant low bandwidth network? That is what I would call "far from optimal".

There is no such thing as 100% uptime or unbreakable RAC. One data center should be the primary and the other one for DR or DW. Received on Thu Jul 09 2009 - 19:35:21 CDT

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