<s>
Capacity	B-General_Concept
optimization	I-General_Concept
is	O
a	O
general	O
term	O
for	O
technologies	O
used	O
to	O
improve	O
storage	O
use	O
by	O
shrinking	O
stored	O
data	O
.	O
</s>
<s>
Primary	O
technologies	O
used	O
for	O
capacity	B-General_Concept
optimization	I-General_Concept
are	O
data	B-General_Concept
deduplication	I-General_Concept
and	O
data	B-General_Concept
compression	I-General_Concept
.	O
</s>
<s>
Typically	O
using	O
cryptographic	B-Algorithm
hash	I-Algorithm
functions	I-Algorithm
as	O
identifiers	O
of	O
unique	O
sequences	O
,	O
sequences	O
are	O
compared	O
to	O
the	O
history	O
of	O
other	O
such	O
sequences	O
,	O
and	O
where	O
possible	O
,	O
the	O
first	O
uniquely	O
stored	O
version	O
of	O
a	O
sequence	O
is	O
referenced	O
rather	O
than	O
stored	O
again	O
.	O
</s>
<s>
Different	O
methods	O
for	O
selecting	O
data	O
windows	O
include	O
4KB	O
blocks	O
to	O
full-file	O
comparisons	O
known	O
as	O
single-instance	B-Application
storage	I-Application
(	O
SIS	O
)	O
.	O
</s>
<s>
Capacity	B-General_Concept
optimization	I-General_Concept
generally	O
refers	O
to	O
the	O
use	O
of	O
this	O
kind	O
of	O
technology	O
in	O
a	O
storage	O
system	O
.	O
</s>
<s>
There	O
are	O
also	O
implementations	O
in	O
networking	O
(	O
especially	O
wide-area	O
networking	O
)	O
,	O
where	O
they	O
are	O
sometimes	O
called	O
bandwidth	O
optimization	O
or	O
WAN	B-Protocol
optimization	I-Protocol
.	O
</s>
<s>
Commercial	O
implementations	O
of	O
capacity	B-General_Concept
optimization	I-General_Concept
are	O
most	O
often	O
found	O
in	O
backup/recovery	O
storage	O
,	O
where	O
storage	O
of	O
iterating	O
versions	O
of	O
backups	O
day	O
to	O
day	O
creates	O
an	O
opportunity	O
for	O
reduction	O
in	O
space	O
using	O
this	O
approach	O
.	O
</s>
