Re: HA Clustering with RAC

From: Andreas Schulze <b79xan_at_gmx.de>
Date: 19 Mar 2004 03:31:41 -0800
Message-ID: <5ee46f5c.0403190331.4608ec90_at_posting.google.com>


Ulf.Pralle_at_web.de (Ulf) wrote in message news:<57f997b6.0403180247.11eecb62_at_posting.google.com>...
> Hi guys,
> I'm writing my diploma thesis about Disaster Recovery. I try to differ
> types of cluster depending of the layer where they are realized.
> Here is my point of view:The aim of a cluster is, that there is an
> automatic failover of resources to the secondary site that no
> transaction is lost.This means that the OS, the database and the
> application (e.g. SAP R/3) must be active on the secondary site.
>
> Here are my questions:
> On which layer (OS,DBMS,Application) is the failover realized? Can it
> be realized on different layers?Which application does support this
> function? Or have all applications to support this function?
> Do you always need a special cluster software like HACMP?
>
> I would be glad, if you could answer my questions and give me links
> where I can read something about this.
>
> Bye

Hallo Ulf,

you might start your thesis with getting the definitions of failover/takeover/high availability etc. straight. As you are going to consider clusters in general plus software of different vendors you are likely to experience that some terms are used differently depending on who uses them. High availability as defined by IBM does not mean that there is no downtime. The IBM docs state expressively that HACMP is not the adequate solution if you cannot afford having downtime. I.e. you might use a HACMP cluster for credit card processing (and there may be some minutes when no cards are being processed) but it is not suitable for running a nuclear power plant. Take a look at the IBM redbook site http://www.redbooks.ibm.com/ There is a huge number of pdf docs available (at no cost) that will tell you a lot of what you need to know about IBM HACMP.

Just my 5 cent.
HTH,
Andreas Received on Fri Mar 19 2004 - 12:31:41 CET

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