Re: What are the differences between Real Application Clusters, Guard I and Guard II?

>> The main disadvantage is that RAC depends on the clustering solutions
>> offered by your server manufacturer. This can mean that the nodes in
your
>> cluster need to be physically close together. Hence if you get a
disaster
>> like a fire in your data centre, the entire cluster can be destroyed.
>> Redundant nodes won't save you. I've heard that some operating systems
>> (VMS?) can implement clustering over a wide area. I'd be interested to
>hear
>> from anybody who knows about this.

>I have heard rumours of a RAC in Beijing where the nodes are separated by
>18kms. Quite why anyone would do that, I have no idea. And it could just be
>rumour.

I can clearly see the point to have a cluster span over different builgding, even cities.
If you have RAC on 2 or more servers, they can all go down together (remember 2 years ago in NYC?).

And yes OpenVMS can do it, you can have a cluster (and those are real clusters, the 1st and still the best after over 15 years) with up to 96 nodes spread up to 500 miles apart (I never knew why this limitation in distance though but I would assume it is sufficient for most companies...).

You have one database, and you can split the client load on multiple servers all serving that database. Very scalable, etc, and you don't ever see downtime on your database not even for OS upgrades or hardware maintenance. Of course for Oracle upgrades you have downtime, I don't think there's a way around thats, is there?

-- 
Syltrem

OpenVMS 7.3-1 + Oracle 8.1.7.4
http://pages.infinit.net/syltrem (OpenVMS related web site, en français)
---zulu is not in my email address---