In a previous episode Henrik Nordstrom said...
::
:: Wojtek Sylwestrzak wrote:
::
:: > In practice: do you know of many replicas not being mirrors,
:: > acoording to this definition?
::
:: Not really, a replica is most of the time also a mirror. The exception
:: is when you have two way replication of information and neither of the
:: replicas is the authoritive origin, but I haven't yet seen this model
:: actively used in web services.
::
I work with one of these.. two physical locations where the
applications share an Oracle Database in Replicated Server Mode
(rw).. I'd call that a replica as neither of the sites is
authoritative in any manner.
on the cache vs mirror thing:
in my mind the difference between a cache and a mirror is that in the
cache scenario the cache is responsible for enforcing expiration
information (do I serve my copy or do I get one from the origin
server?), and in the mirror scenario the origin server is responsible
for changing the mirror's copy when appropriate, the mirror never
makes an expiration decision.
focusing on static/dynamic is a red herring and is sometimes an
implementation artifact, but is surely not part of the definition (and
we don't want to un-wittingly create a limitation because it happens
to be a side-effect of current practice..)
-P
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