<s>
Scalability	B-Architecture
is	O
the	O
property	O
of	O
a	O
system	O
to	O
handle	O
a	O
growing	O
amount	O
of	O
work	O
.	O
</s>
<s>
In	O
an	O
economic	O
context	O
,	O
a	O
scalable	B-Architecture
business	O
model	O
implies	O
that	O
a	O
company	O
can	O
increase	O
sales	O
given	O
increased	O
resources	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
package	O
delivery	O
system	O
is	O
scalable	B-Architecture
because	O
more	O
packages	O
can	O
be	O
delivered	O
by	O
adding	O
more	O
delivery	O
vehicles	O
.	O
</s>
<s>
However	O
,	O
if	O
all	O
packages	O
had	O
to	O
first	O
pass	O
through	O
a	O
single	O
warehouse	O
for	O
sorting	O
,	O
the	O
system	O
would	O
not	O
be	O
as	O
scalable	B-Architecture
,	O
because	O
one	O
warehouse	O
can	O
handle	O
only	O
a	O
limited	O
number	O
of	O
packages	O
.	O
</s>
<s>
In	O
computing	O
,	O
scalability	B-Architecture
is	O
a	O
characteristic	O
of	O
computers	O
,	O
networks	O
,	O
algorithms	O
,	O
networking	O
protocols	O
,	O
programs	B-Application
and	O
applications	O
.	O
</s>
<s>
An	O
example	O
is	O
a	O
search	B-Application
engine	I-Application
,	O
which	O
must	O
support	O
increasing	O
numbers	O
of	O
users	O
,	O
and	O
the	O
number	O
of	O
topics	O
it	O
indexes	O
.	O
</s>
<s>
Webscale	B-Architecture
is	O
a	O
computer	O
architectural	O
approach	O
that	O
brings	O
the	O
capabilities	O
of	O
large-scale	O
cloud	O
computing	O
companies	O
into	O
enterprise	O
data	O
centers	O
.	O
</s>
<s>
In	O
distributed	B-Architecture
systems	I-Architecture
,	O
there	O
are	O
several	O
definitions	O
according	O
to	O
the	O
authors	O
,	O
some	O
considering	O
the	O
concepts	O
of	O
scalability	B-Architecture
a	O
sub-part	O
of	O
elasticity	O
,	O
others	O
as	O
being	O
distinct	O
.	O
</s>
<s>
In	O
mathematics	O
,	O
scalability	B-Architecture
mostly	O
refers	O
to	O
closure	O
under	O
scalar	O
multiplication	O
.	O
</s>
<s>
In	O
industrial	O
engineering	O
and	O
manufacturing	O
,	O
scalability	B-Architecture
refers	O
to	O
the	O
capacity	O
of	O
a	O
process	O
,	O
system	O
,	O
or	O
organization	O
to	O
handle	O
a	O
growing	O
workload	O
,	O
adapt	O
to	O
increasing	O
demands	O
,	O
and	O
maintain	O
operational	O
efficiency	O
.	O
</s>
<s>
A	O
scalable	B-Architecture
system	I-Architecture
can	O
effectively	O
manage	O
increased	O
production	O
volumes	O
,	O
new	O
product	O
lines	O
,	O
or	O
expanding	O
markets	O
without	O
compromising	O
quality	O
or	O
performance	O
.	O
</s>
<s>
In	O
this	O
context	O
,	O
scalability	B-Architecture
is	O
a	O
vital	O
consideration	O
for	O
businesses	O
aiming	O
to	O
meet	O
customer	O
expectations	O
,	O
remain	O
competitive	O
,	O
and	O
achieve	O
sustainable	O
growth	O
.	O
</s>
<s>
Factors	O
influencing	O
scalability	B-Architecture
include	O
the	O
flexibility	O
of	O
the	O
production	O
process	O
,	O
the	O
adaptability	O
of	O
the	O
workforce	O
,	O
and	O
the	O
integration	O
of	O
advanced	O
technologies	O
.	O
</s>
<s>
By	O
implementing	O
scalable	B-Architecture
solutions	O
,	O
companies	O
can	O
optimize	O
resource	O
utilization	O
,	O
reduce	O
costs	O
,	O
and	O
streamline	O
their	O
operations	O
.	O
</s>
<s>
Scalability	B-Architecture
in	O
industrial	O
engineering	O
and	O
manufacturing	O
enables	O
businesses	O
to	O
respond	O
to	O
fluctuating	O
market	O
conditions	O
,	O
capitalize	O
on	O
emerging	O
opportunities	O
,	O
and	O
thrive	O
in	O
an	O
ever-evolving	O
global	O
landscape	O
.	O
</s>
<s>
Scalability	B-Architecture
can	O
be	O
measured	O
over	O
multiple	O
dimensions	O
,	O
such	O
as	O
:	O
</s>
<s>
Administrative	O
scalability	B-Architecture
:	O
The	O
ability	O
for	O
an	O
increasing	O
number	O
of	O
organizations	O
or	O
users	O
to	O
access	O
a	O
system	O
.	O
</s>
<s>
Functional	O
scalability	B-Architecture
:	O
The	O
ability	O
to	O
enhance	O
the	O
system	O
by	O
adding	O
new	O
functionality	O
without	O
disrupting	O
existing	O
activities	O
.	O
</s>
<s>
Geographic	O
scalability	B-Architecture
:	O
The	O
ability	O
to	O
maintain	O
effectiveness	O
during	O
expansion	O
from	O
a	O
local	O
area	O
to	O
a	O
larger	O
region	O
.	O
</s>
<s>
Load	O
scalability	B-Architecture
:	O
The	O
ability	O
for	O
a	O
distributed	B-Architecture
system	I-Architecture
to	O
expand	O
and	O
contract	O
to	O
accommodate	O
heavier	O
or	O
lighter	O
loads	O
,	O
including	O
,	O
the	O
ease	O
with	O
which	O
a	O
system	O
or	O
component	O
can	O
be	O
modified	O
,	O
added	O
,	O
or	O
removed	O
,	O
to	O
accommodate	O
changing	O
loads	O
.	O
</s>
<s>
Generation	O
scalability	B-Architecture
:	O
The	O
ability	O
of	O
a	O
system	O
to	O
scale	O
by	O
adopting	O
new	O
generations	O
of	O
components	O
.	O
</s>
<s>
Heterogeneous	O
scalability	B-Architecture
is	O
the	O
ability	O
to	O
adopt	O
components	O
from	O
different	O
vendors	O
.	O
</s>
<s>
A	O
routing	B-Protocol
protocol	I-Protocol
is	O
considered	O
scalable	B-Architecture
with	O
respect	O
to	O
network	O
size	O
,	O
if	O
the	O
size	O
of	O
the	O
necessary	O
routing	B-Protocol
table	I-Protocol
on	O
each	O
node	O
grows	O
as	O
O(log N )	O
,	O
where	O
N	O
is	O
the	O
number	O
of	O
nodes	O
in	O
the	O
network	O
.	O
</s>
<s>
Some	O
early	O
peer-to-peer	O
(	O
P2P	O
)	O
implementations	O
of	O
Gnutella	B-Protocol
had	O
scaling	B-Architecture
issues	O
.	O
</s>
<s>
Each	O
node	O
query	O
flooded	B-Protocol
its	O
requests	O
to	O
all	O
nodes	O
.	O
</s>
<s>
Other	O
P2P	O
systems	O
like	O
BitTorrent	B-Protocol
scale	O
well	O
because	O
the	O
demand	O
on	O
each	O
peer	O
is	O
independent	O
of	O
the	O
number	O
of	O
peers	O
.	O
</s>
<s>
A	O
scalable	B-Architecture
online	B-General_Concept
transaction	I-General_Concept
processing	I-General_Concept
system	O
or	O
database	B-Application
management	I-Application
system	I-Application
is	O
one	O
that	O
can	O
be	O
upgraded	O
to	O
process	O
more	O
transactions	O
by	O
adding	O
new	O
processors	O
,	O
devices	O
and	O
storage	O
,	O
and	O
which	O
can	O
be	O
upgraded	O
easily	O
and	O
transparently	O
without	O
shutting	O
it	O
down	O
.	O
</s>
<s>
The	O
distributed	O
nature	O
of	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
allows	O
it	O
to	O
work	O
efficiently	O
,	O
serving	O
billions	O
of	O
hosts	B-Application
on	O
the	O
worldwide	O
Internet	O
.	O
</s>
<s>
Scaling	B-Architecture
horizontally	O
(	O
out/in	O
)	O
means	O
adding	O
more	O
nodes	O
to	O
(	O
or	O
removing	O
nodes	O
from	O
)	O
a	O
system	O
,	O
such	O
as	O
adding	O
a	O
new	O
computer	O
to	O
a	O
distributed	B-Architecture
software	I-Architecture
application	O
.	O
</s>
<s>
An	O
example	O
might	O
involve	O
scaling	B-Architecture
out	O
from	O
one	O
web	O
server	O
to	O
three	O
.	O
</s>
<s>
High-performance	B-Architecture
computing	I-Architecture
applications	O
,	O
such	O
as	O
seismic	O
analysis	O
and	O
biotechnology	O
,	O
scale	O
workloads	O
horizontally	O
to	O
support	O
tasks	O
that	O
once	O
would	O
have	O
required	O
expensive	O
supercomputers	B-Architecture
.	O
</s>
<s>
Other	O
workloads	O
,	O
such	O
as	O
large	O
social	O
networks	O
,	O
exceed	O
the	O
capacity	O
of	O
the	O
largest	O
supercomputer	B-Architecture
and	O
can	O
only	O
be	O
handled	O
by	O
scalable	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Exploiting	O
this	O
scalability	B-Architecture
requires	O
software	O
for	O
efficient	O
resource	O
management	O
and	O
maintenance	O
.	O
</s>
<s>
Scaling	B-Architecture
vertically	O
(	O
up/down	O
)	O
means	O
adding	O
resources	O
to	O
(	O
or	O
removing	O
resources	O
from	O
)	O
a	O
single	O
node	O
,	O
typically	O
involving	O
the	O
addition	O
of	O
CPUs	O
,	O
memory	O
or	O
storage	O
to	O
a	O
single	O
computer	O
.	O
</s>
<s>
Larger	O
numbers	O
of	O
elements	O
increases	O
management	O
complexity	O
,	O
more	O
sophisticated	O
programming	O
to	O
allocate	O
tasks	O
among	O
resources	O
and	O
handle	O
issues	O
such	O
as	O
throughput	O
and	O
latency	O
across	O
nodes	O
,	O
while	O
some	O
applications	B-Operating_System
do	I-Operating_System
not	I-Operating_System
scale	I-Operating_System
horizontally	I-Operating_System
.	O
</s>
<s>
Network	B-Architecture
function	I-Architecture
virtualization	I-Architecture
defines	O
these	O
terms	O
differently	O
:	O
scaling	B-Architecture
out/in	O
is	O
the	O
ability	O
to	O
scale	O
by	O
adding/removing	O
resource	O
instances	O
(	O
e.g.	O
,	O
virtual	O
machine	O
)	O
,	O
whereas	O
scaling	B-Architecture
up/down	O
is	O
the	O
ability	O
to	O
scale	O
by	O
changing	O
allocated	O
resources	O
(	O
e.g.	O
,	O
memory/CPU/storage	O
capacity	O
)	O
.	O
</s>
<s>
Scalability	B-Architecture
for	O
databases	B-Application
requires	O
that	O
the	O
database	B-Application
system	I-Application
be	O
able	O
to	O
perform	O
additional	O
work	O
given	O
greater	O
hardware	O
resources	O
,	O
such	O
as	O
additional	O
servers	O
,	O
processors	O
,	O
memory	O
and	O
storage	O
.	O
</s>
<s>
Workloads	O
have	O
continued	O
to	O
grow	O
and	O
demands	O
on	O
databases	B-Application
have	O
followed	O
suit	O
.	O
</s>
<s>
Algorithmic	O
innovations	O
have	O
include	O
row-level	O
locking	B-Operating_System
and	O
table	O
and	O
index	O
partitioning	O
.	O
</s>
<s>
Architectural	O
innovations	O
include	O
shared-nothing	B-Operating_System
and	O
shared-everything	O
architectures	O
for	O
managing	O
multi-server	O
configurations	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
scale-out	B-Architecture
data	B-General_Concept
storage	I-General_Concept
,	O
scalability	B-Architecture
is	O
defined	O
as	O
the	O
maximum	O
storage	O
cluster	O
size	O
which	O
guarantees	O
full	O
data	O
consistency	O
,	O
meaning	O
there	O
is	O
only	O
ever	O
one	O
valid	O
version	O
of	O
stored	O
data	O
in	O
the	O
whole	O
cluster	O
,	O
independently	O
from	O
the	O
number	O
of	O
redundant	O
physical	O
data	O
copies	O
.	O
</s>
<s>
Clusters	O
which	O
provide	O
"	O
lazy	O
"	O
redundancy	O
by	O
updating	O
copies	O
in	O
an	O
asynchronous	O
fashion	O
are	O
called	O
'	B-General_Concept
eventually	I-General_Concept
consistent	I-General_Concept
 '	I-General_Concept
.	O
</s>
<s>
This	O
type	O
of	O
scale-out	B-Architecture
design	O
is	O
suitable	O
when	O
availability	O
and	O
responsiveness	O
are	O
rated	O
higher	O
than	O
consistency	O
,	O
which	O
is	O
true	O
for	O
many	O
web	O
file-hosting	O
services	O
or	O
web	O
caches	O
(	O
if	O
you	O
want	O
the	O
latest	O
version	O
,	O
wait	O
some	O
seconds	O
for	O
it	O
to	O
propagate	O
)	O
.	O
</s>
<s>
Many	O
open-source	O
and	O
even	O
commercial	O
scale-out	B-Architecture
storage	O
clusters	O
,	O
especially	O
those	O
built	O
on	O
top	O
of	O
standard	O
PC	O
hardware	O
and	O
networks	O
,	O
provide	O
eventual	B-General_Concept
consistency	I-General_Concept
only	O
.	O
</s>
<s>
Idem	O
some	O
NoSQL	B-General_Concept
databases	B-Application
like	O
CouchDB	B-Application
and	O
others	O
mentioned	O
above	O
.	O
</s>
<s>
Indicators	O
for	O
eventually	B-General_Concept
consistent	I-General_Concept
designs	O
(	O
not	O
suitable	O
for	O
transactional	O
applications	O
!	O
)	O
</s>
<s>
It	O
is	O
often	O
advised	O
to	O
focus	O
system	O
design	O
on	O
hardware	O
scalability	B-Architecture
rather	O
than	O
on	O
capacity	O
.	O
</s>
<s>
It	O
is	O
typically	O
cheaper	O
to	O
add	O
a	O
new	O
node	O
to	O
a	O
system	O
in	O
order	O
to	O
achieve	O
improved	O
performance	O
than	O
to	O
partake	O
in	O
performance	B-Device
tuning	I-Device
to	O
improve	O
the	O
capacity	O
that	O
each	O
node	O
can	O
handle	O
.	O
</s>
<s>
But	O
this	O
approach	O
can	O
have	O
diminishing	O
returns	O
(	O
as	O
discussed	O
in	O
performance	B-General_Concept
engineering	I-General_Concept
)	O
.	O
</s>
<s>
If	O
is	O
the	O
fraction	O
of	O
a	O
calculation	O
that	O
is	O
sequential	O
,	O
and	O
is	O
the	O
fraction	O
that	O
can	O
be	O
parallelized	O
,	O
the	O
maximum	O
speedup	B-Operating_System
that	O
can	O
be	O
achieved	O
by	O
using	O
P	O
processors	O
is	O
given	O
according	O
to	O
Amdahl	B-Operating_System
's	I-Operating_System
Law	I-Operating_System
:	O
</s>
<s>
High	B-Architecture
performance	I-Architecture
computing	I-Architecture
has	O
two	O
common	O
notions	O
of	O
scalability	B-Architecture
:	O
</s>
<s>
Strong	O
scaling	B-Architecture
is	O
defined	O
as	O
how	O
the	O
solution	O
time	O
varies	O
with	O
the	O
number	O
of	O
processors	O
for	O
a	O
fixed	O
total	O
problem	O
size	O
.	O
</s>
<s>
Weak	O
scaling	B-Architecture
is	O
defined	O
as	O
how	O
the	O
solution	O
time	O
varies	O
with	O
the	O
number	O
of	O
processors	O
for	O
a	O
fixed	O
problem	O
size	O
per	O
processor	O
.	O
</s>
