Clark Lowery wrote:
We are beginning the construction of a third data center, and I've been
tasked with developing our mainframe configuration plan.
I would like to run a true data sharing Geoplex (hot/hot, with load
distribution done by our foundry devices behind the WEB servers).
In talking to IBM, I've been given data about how elapsed time increases by
kilometer across fiber, and warned about CF delays if we go more than a
kilometer or two.
While the physics of the latency are clear, what I'm not convinced of is
the impact on my users. Since total DB2 processing is a very tiny portion
of the overall service time, I can't see any latency measured in
microseconds impacting users.
BUT...
What do I have to watch out for internal to DB2 and z/os? For example, will
I need more capacity to handle overhead lock management costs?
I've received some help for a few people who've done something similar, but
we'll be using EMC for data replication and I've found no one running a
Geoplex supported by EMC's SRDF/A.
Any help would be greatly appreciated!!!
Not a Sysplex guy, but I am a network guy.
It not necessary the latency, it's also the number of requests going
between the two. One request with a couple of microseconds of latency
is not going to be noticed, but a few thousand of them in a short time
period will be.
I am not sure if any of the information flowing between the CEC’s and
the CF’s are synchronous, but if they are (I would assume there would be
some) that will be noticed.
The other thing to look at is where is the new Data Center is in
relationship to the web servers. If current the web servers are in the
same data center as your current mainframe is and now you have a new
mainframe that is not there, you are also going to see a performance hit
there.
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