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doc: explain "architecture"
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Thomas Schoebel-Theuer
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@ -418,6 +418,228 @@ reference "chap:LV-Football"
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with each of the fundamental models mentioned here.
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\end_layout
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\begin_layout Section
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What is Architecture
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\begin_inset CommandInset label
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LatexCommand label
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name "sec:What-is-Architecture"
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\end_inset
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\end_layout
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\begin_layout Standard
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From
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\begin_inset Flex URL
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status open
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\begin_layout Plain Layout
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https://en.wikipedia.org/wiki/Software_architecture
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\end_layout
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\end_inset
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:
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\end_layout
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\begin_layout Quote
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Software architecture refers to the
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\series bold
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high level structures
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\series default
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of a software system and the
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\series bold
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discipline
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\series default
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of creating such structures and systems.
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\end_layout
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\begin_layout Standard
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Throughout this paper, the term
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\begin_inset Quotes eld
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\end_inset
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architecture
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\begin_inset Quotes erd
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\end_inset
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is strictly separated from
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\begin_inset Quotes eld
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\end_inset
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implementations
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\begin_inset Quotes erd
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\end_inset
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.
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Any of
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\begin_inset Quotes eld
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\end_inset
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architecture
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\begin_inset Quotes erd
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\end_inset
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or
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\begin_inset Quotes eld
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\end_inset
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implementation
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\begin_inset Quotes erd
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\end_inset
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can relate to both hard- and software in general.
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Graphics
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filename images/MatieresCorrosives.png
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lyxscale 50
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scale 17
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\end_inset
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Confusion of
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\begin_inset Quotes eld
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\end_inset
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architecture
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\begin_inset Quotes erd
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\end_inset
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with
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\begin_inset Quotes eld
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\end_inset
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implementation
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\begin_inset Quotes erd
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\end_inset
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is a major source of ill-designs, which then often cause major product
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flaws and/or operational problems.
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Be sure to understand the difference.
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Graphics
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filename images/MatieresCorrosives.png
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lyxscale 50
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scale 17
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\end_inset
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Another source of costly ill-designs is starting with a particular implementatio
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n in mind, and not sufficiently reasoning abouts its fundamental architecture.
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Graphics
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filename images/lightbulb_brightlit_benj_.png
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lyxscale 12
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scale 7
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\end_inset
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Recommended best practice is to (1) look at the
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\series bold
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problem space
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\series default
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, then (2) consider a
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\emph on
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set
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\emph default
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of
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\series bold
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architectural solution classes
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\series default
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, and (3) look at the
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\series bold
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mappings
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\series default
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between them.
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This means: start with
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\series bold
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architectural requirements
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\series default
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for a particular
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\series bold
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application area
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\series default
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(typically covering
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\emph on
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multiple
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\emph default
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use cases), then look at
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\series bold
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multiple solution architectures
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\series default
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, and finally go down to a
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\series bold
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\emph on
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set
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\series default
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\emph default
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of potential implementations, but only
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\emph on
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after
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\emph default
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the former has been understood.
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Graphics
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filename images/MatieresCorrosives.png
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lyxscale 50
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scale 17
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\end_inset
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Starting with a particular single solution in mind is almost a
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\emph on
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guarantee
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\emph default
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for a non-optimum solution, or even a failed project, or even a disaster
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at company level when
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\series bold
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enterprise-critical mass data
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\series default
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is involved.
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Graphics
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filename images/lightbulb_brightlit_benj_.png
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lyxscale 12
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scale 7
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\end_inset
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Nevertheless, don't think in waterfall models.
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Always work
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\series bold
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iteratively
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\series default
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and
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\series bold
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evolutionary
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\series default
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, but nevertheless obey the principle that any bug in an architectural ill-desig
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n cannot be fixed by the best implementation of the world.
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Be sure to understand the fundamental difference between architecture and
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its (multiple / alternative) implemenations by their respective
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\series bold
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reach
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\series default
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.
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\end_layout
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\begin_layout Section
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What is
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\emph on
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@ -3842,7 +4064,14 @@ Datacenters aren't usually operated for fun or for hobby.
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\emph on
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architecture
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\emph default
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is very important, because it can seriously limit your business.
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(cf section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:What-is-Architecture"
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\end_inset
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) is very important, because it can seriously limit your business.
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Overcoming architectural ill-designs can grow extremely cumbersome and
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costly.
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\end_layout
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@ -7968,8 +8197,15 @@ Choosing the wrong layer for
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mass data replication
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\series default
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may get you into trouble.
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Here is an explanation why replication at the block layer is more easy
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and less error prone:
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Here is an architectural-level (cf section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:What-is-Architecture"
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\end_inset
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) explanation why replication at the block layer is more easy and less error
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prone:
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\end_layout
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\begin_layout Standard
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@ -8274,6 +8510,65 @@ This way of thinking and acting is completely broken, and can endanger both
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companies and careers.
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\end_layout
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\begin_layout Standard
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This is not only because of confusion of
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\begin_inset Quotes eld
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\end_inset
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architecture
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\begin_inset Quotes erd
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\end_inset
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with
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\begin_inset Quotes eld
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\end_inset
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implementation
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\begin_inset Quotes erd
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\end_inset
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, cf section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:What-is-Architecture"
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\end_inset
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.
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It is also fundamentally broken because it assumes some
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\begin_inset Quotes eld
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\end_inset
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linearity
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\begin_inset Quotes erd
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\end_inset
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in a field which is non-linear
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\emph on
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by definition
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\emph default
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.
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If scalability would be linear, the term would not be useful at all, because
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there would be
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\emph on
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no limit
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\emph default
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.
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However, limits exist in practice, and the term
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\begin_inset Quotes eld
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\end_inset
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scalability
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\begin_inset Quotes erd
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\end_inset
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is the
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\emph on
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means
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\emph default
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for describing the behaviour at or around the limit.
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\end_layout
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\begin_layout Standard
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Another
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\emph on
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@ -8283,7 +8578,7 @@ incorrect
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\begin_inset Quotes eld
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\end_inset
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scalablity
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scalability
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\begin_inset Quotes erd
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\end_inset
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@ -10154,9 +10449,15 @@ name "subsec:Filesystem-Layer-vs"
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\end_layout
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\begin_layout Standard
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Following factors are responsible for better architectural scalability of
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the block layer vs the filesystem layer, at least in many cases, with a
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few exceptions (list may be incomplete):
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Following factors are responsible for better architectural (cf section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:What-is-Architecture"
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\end_inset
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) scalability of the block layer vs the filesystem layer, at least in many
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cases, with a few exceptions (list may be incomplete):
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\end_layout
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\begin_layout Enumerate
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@ -10589,7 +10890,14 @@ overall
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\begin_inset Newline newline
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\end_inset
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An impressive example for ill-design can be found in section
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An impressive example for architectural (cf section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:What-is-Architecture"
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\end_inset
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) ill-design can be found in section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "subsec:Example-Failures-of"
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