Two things to consider:
1. Distance => delay. For long distances it means synchronous copy is
not applicable. It can be asynchronous copy or some kind of "fuzzy" copy
like PPRC-XD or SRDF Adaptive Copy.
2. Bandwidth and I/O rate. The more I/O the higher bandwidth is needed
for replication. Temporary spikes are managed by "delta", but it doesn't
mean you can do a lot of I/O during business hours and rebalance delta
on evening. It is complex topic, especially when fuzzy copy is considered.
BTW: Before you start you can establish some POC configuration. There
are devices simulating distance (delay) and bandwidth limitation. So,
you can have 9000 miles in single computer room.
Note: it is not 9000 miles of fiber optic in a suitcase - such devices
are actually used for much shorter distances (10-20km) and rather for
synchronous copy.
--
Radoslaw Skorupka
(looking for new job)
Lodz, Poland
W dniu 21.05.2021 o 21:34, Cameron Conacher pisze:
Hello folks,
I am trying to find out what we could consider to be a "safe" maximum
distance for mirroring DASD from one site to another.
We have a situation where site #1 will be thousands (9,000) of miles away
from site #2 (across the ocean.
I realize there would be a great deal of latency involved.
But is this even possible or is it simply a non-starter?
The second question I have is, suppose that I waved a magic wand and
suddenly all my data was sitting comfortably in site #2.
Could I (again ignoring latency for the moment) run a batch JOB or CICS
transactions in site #1 that accessed the data 9,000 miles away in site #2?
My thought here was if the data must absolutely be relocated, and
people are willing to accept there will be latency, can we just access the
DASD at site #2, rather than building a large data centre and performing
all of the processing in site #2?
Even if we run the processing at site #2, there will be many interfaces
between site #1 and site #2.
I know there are hard distance limitations.
I think Global Mirror is limited to about 1500 miles.
And I would hazard a guess that remote DASD would not be viable either.
But I wanted to see if someone really "knows", rather than something I may
have mis-remembered.
Any thoughts/opinions are appreciated.
Thanks
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