From: Mike '/m' 


Look into OpenVMS clustering.  The nodes of the cluster can be
geographically distant.

 /m

On Sun, 05 Jun 2005 15:49:45 -0700, Ellen K.  wrote:

>Well, after a little more reading, I don't think clustering is going to
>be my answer.  If I correctly understood what I read, clustering means
>the clustered machines all use ONE set of data.  So it protects against
>machine failure and network failure but if the location where the data
>reside goes down for whatever reason what good are the additional boxes?
>(Our L.A. location is obviously vulnerable to earthquakes, and not so
>obviously vulnerable to terrorist attack of several nearby institutions,
>and TJ, well, it's in Mexico, nuff said.)  I think we want redundancy of
>the DATA in addition to being protected against machine failure and
>network failure.
>
>Log shipping (similar to replication but specifically designed for when
>you want a standby server, for example there are stored procedures for
>making the standby the primary etc) seems more like what I want except
>that for my recordings database it isn't going to be a solution because
>BLOB data are actually stored on their own pages, all that's in the BLOB
>field is the pointer to the location of the data, and the BLOB data per
>se are not written to the log.   I haven't seen anything about whether
>BLOB data are propagated if we go back to my original idea of
>transactional replication, that's my next piece of research.
>
>My boss agreed that using replication with the idea of changing the IP
>number of the Subscriber wouldn't work because they will be on different
>subnets, but suggested that instead of changing the IP number of the
>Subscriber, change the *applications* to point to the Subscriber instead
>of the Publisher.  On further thought it seems to me that since we're
>going with this Enterprise Service Bus thing we could have something
>that sends a message with the new location to point to, and/or have the
>connection string somewhere in the middle tier so we could change it in
>the event of a disaster, and this would be transparent to the users.
>
>Comments?

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