mirror of https://github.com/schoebel/mars
doc: new section What is an Object Store
This commit is contained in:
Thomas Schoebel-Theuer
Thomas Schoebel-Theuer
parent
1b0c365759
commit
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#FIG 3.2 Produced by xfig version 3.2.8a
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Landscape
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Center
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Metric
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100.00
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Single
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-2
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1200 2
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1 2 0 3 12 7 50 -1 -1 0.000 1 0.0000 1687 1125 1237 675 450 1125 2924 1125
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1 2 0 3 27 7 50 -1 -1 0.000 1 0.0000 1957 1125 1057 630 900 1755 3015 495
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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2 1 1.00 60.00 120.00
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945 1800 720 1215
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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2 1 1.00 60.00 120.00
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3015 1440 2970 1125
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4 1 12 50 -1 18 12 0.0000 4 195 2280 1215 405 Filesystem Functionality\001
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4 0 0 50 -1 16 10 0.0000 4 150 1395 945 1980 only in Filesystems\001
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4 0 0 50 -1 16 10 0.0000 4 150 1515 3015 1530 only in Object Stores\001
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4 1 12 50 -1 18 12 0.0000 4 195 675 1215 225 Typical\001
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4 1 1 50 -1 18 10 0.0000 4 150 1830 1935 1170 Common Functionality\001
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4 1 27 50 -1 18 11 0.0000 4 180 615 3780 585 Typical\001
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4 0 27 50 -1 18 11 0.0000 4 180 2205 2835 765 Object Store Functionality\001
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@ -4205,6 +4205,390 @@ noprefix "false"
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.
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\end_layout
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\begin_layout Section
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What is an Object Store
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\begin_inset CommandInset label
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LatexCommand label
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name "sec:What-is-Object-Store"
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\end_inset
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\end_layout
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\begin_layout Standard
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The following picture explains the typical
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\series bold
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Abstract Functionality
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\series default
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differences between contemporary object store
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\emph on
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implementations
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\emph default
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and contemporary filesystem
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\emph on
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implementations
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\emph default
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.
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\end_layout
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\begin_layout Standard
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\noindent
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\align center
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\begin_inset Graphics
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filename images/functionality-object-store-vs-filesystems.fig
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width 70col%
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\end_inset
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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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Caution: there exists a large bandwidth of object store implementations,
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as well as filesystem implementations (e.g.
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academic prototypes vs industrial).
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The sizes of the above
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\emph on
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typical
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\emph default
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areas
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\emph on
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cannot
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\emph default
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tell you too much about
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\emph on
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implementation efforts
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\emph default
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as well as
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\emph on
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maintenance efforts
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\emph default
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and other efforts, because other factors like
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\series bold
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strongly coupled vs loosely coupled
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\series default
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implementations /
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\emph on
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ease
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\emph default
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of caching e.g.
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in
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\series bold
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Cache Coherence
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\series default
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problems / other architectural differences /
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\series bold
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Consistency Models
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\series default
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/ experiences of protagonists /
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\series bold
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maturity
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\series default
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at multiple layers and on subsystems / size of the
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\series bold
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developer community
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\series default
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e.g.
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in small vs big projects like the Linux kernel / common code e.g.
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among multiple Linux filesystem implementions / etc are
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\emph on
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typically
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\emph default
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much more important.
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While well-known classical filesystems are mature technology on tightly
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coupled local
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\begin_inset Foot
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status open
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\begin_layout Plain Layout
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For
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\begin_inset Quotes eld
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\end_inset
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Distributed Systems
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\begin_inset Quotes erd
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\end_inset
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, we don't count low-level
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\begin_inset Quotes eld
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\end_inset
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local
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\begin_inset Quotes erd
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\end_inset
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connections like
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\series bold
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short-distance
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\series default
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SAS cables between disk enclosures and servers.
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\end_layout
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\begin_layout Plain Layout
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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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Attention: some evangelists are wrongly claiming that local storage would
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be
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\begin_inset Quotes eld
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\end_inset
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too small
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\begin_inset Quotes erd
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\end_inset
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and/or
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\begin_inset Quotes eld
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\end_inset
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unmanagle
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\begin_inset Quotes erd
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\end_inset
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/ etc for too many use cases.
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Notice: contemporary
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\begin_inset Quotes eld
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\end_inset
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local
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\begin_inset Quotes erd
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\end_inset
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hardware RAID networks can easily scale up to 1 petabytes or more, and
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can provide competitive IOPS rates.
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\end_layout
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\end_inset
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servers, object stores often try to be
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\begin_inset Quotes eld
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\end_inset
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sexy
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\begin_inset Quotes erd
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\end_inset
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and
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\begin_inset Quotes eld
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\end_inset
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more intelligent
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\begin_inset Quotes erd
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\end_inset
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by
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\begin_inset Quotes eld
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\end_inset
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less functionality at the surface
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\begin_inset Quotes erd
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\end_inset
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on loosely coupled BigCluster designs.
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In reality, the latter are typically
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\series bold
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more cumbersome
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\series default
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due to
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\series bold
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less controllable
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\series default
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concepts like
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\begin_inset Quotes eld
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\end_inset
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eventually consistent
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\begin_inset Quotes erd
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\end_inset
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or
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\series bold
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high complexity
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\series default
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, e.g.
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in Distributed Systems / at
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\emph on
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hidden
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\emph default
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parts / less visible subsystems, leading to various problems in practice.
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\end_layout
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\begin_layout Standard
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More details can be found in section
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\begin_inset CommandInset ref
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LatexCommand nameref
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reference "par:Negative-Example:-object"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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.
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\end_layout
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\begin_layout Standard
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\begin_inset VSpace defskip
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\end_inset
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\end_layout
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\begin_layout Standard
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\noindent
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\begin_inset Flex Custom Color Box 3
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status open
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\begin_layout Plain Layout
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\noindent
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\begin_inset Argument 1
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status open
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\begin_layout Plain Layout
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\series bold
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\emph on
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Real
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\emph default
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Functionality and TCO behind typical Object Stores
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\end_layout
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\end_inset
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\begin_inset Graphics
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filename images/lightbulb_brightlit_benj_.png
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lyxscale 9
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scale 5
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\end_inset
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\emph on
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Typical
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\emph default
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object store implementations are approximately nothing else but
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\series bold
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special cases
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\series default
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of classical fileystems, when looking at the
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\emph on
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abstract
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\emph default
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functionality.
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In reality, their
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\begin_inset Quotes eld
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\end_inset
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additional
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\begin_inset Quotes erd
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\end_inset
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functionality is close to neglectible.
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\end_layout
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\begin_layout Plain Layout
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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 9
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scale 5
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\end_inset
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In many cases, roughly comparable classical filesystems are
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\series bold
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more mature
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\series default
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, and/or
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\series bold
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more reliable
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\series default
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, and/or
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\series bold
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cheaper
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\series default
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in terms of TCO = Total Cost of Ownership.
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\end_layout
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\begin_layout Plain Layout
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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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Don't let
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\series bold
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fool
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\series default
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you from contrary generalized claims.
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\series bold
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Always check
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\series default
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such claims in detail, and by
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\emph on
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real experts
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\emph default
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who really know and can not only explain the differences both in terms
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of
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\series bold
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Abstract Functionality
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\series default
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, but also by knowledge and by enough
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\emph on
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first-hand
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\emph default
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experience on
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\emph on
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implementation details
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\emph default
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.
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\end_layout
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\begin_layout Plain Layout
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\begin_inset Graphics
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filename images/lightbulb_brightlit_benj_.png
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lyxscale 9
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scale 5
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\end_inset
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When unsure, read the details from section
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\begin_inset CommandInset ref
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LatexCommand nameref
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reference "par:Negative-Example:-object"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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.
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Chapter
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Architectural Principles and Properties
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\begin_inset CommandInset label
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@ -9170,9 +9554,12 @@ separate
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\end_inset
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In comparison, creating a different interface for an already existing sub-funct
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ionality, and optionally adding some metadata harvesters and filters, is
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requiring much lower
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In comparison, creating a different interface for an
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\emph on
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already existing
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\emph default
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sub-functionality, and optionally adding some metadata harvesters and filters,
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is requiring lower
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\begin_inset Foot
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status open
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@ -11165,8 +11552,8 @@ risk
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\emph on
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known
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\emph default
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to filesystem and database implementers and their architects, provided
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they also know the
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to filesystem and database implementers and their experienced architects,
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provided they also know the
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\series bold
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Theory of Databases
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\series default
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@ -11198,8 +11585,17 @@ extremely big
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\series bold
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eventually consistent
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\series default
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object stores, independently from local vs distributed types of object
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stores.
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object stores (see section
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\begin_inset CommandInset ref
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LatexCommand nameref
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reference "sec:What-is-Object-Store"
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plural "false"
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caps "false"
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noprefix "false"
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\end_inset
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), independently from local vs distributed types of object stores.
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\end_layout
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\begin_layout Standard
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@ -11555,7 +11951,7 @@ Referential Integrity
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wrong
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\emph default
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objects, potentially belonging to other customers, thus breaching privacy
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/ security / etc).
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/ security / isolation / etc).
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\end_layout
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\begin_layout Itemize
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