<s>
Content-addressable	B-Data_Structure
storage	I-Data_Structure
(	O
CAS	O
)	O
,	O
also	O
referred	O
to	O
as	O
content-addressed	O
storage	O
or	O
fixed-content	O
storage	O
,	O
is	O
a	O
way	O
to	O
store	O
information	O
so	O
it	O
can	O
be	O
retrieved	O
based	O
on	O
its	O
content	O
,	O
not	O
its	O
name	O
or	O
location	O
.	O
</s>
<s>
It	O
has	O
been	O
used	O
for	O
high-speed	O
storage	O
and	O
retrieval	B-Library
of	O
fixed	O
content	O
,	O
such	O
as	O
documents	O
stored	O
for	O
compliance	O
with	O
government	O
regulations	O
.	O
</s>
<s>
Content-addressable	B-Data_Structure
storage	I-Data_Structure
is	O
similar	O
to	O
content-addressable	B-Data_Structure
memory	I-Data_Structure
.	O
</s>
<s>
CAS	O
systems	O
work	O
by	O
passing	O
the	O
content	O
of	O
the	O
file	O
through	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
to	O
generate	O
a	O
unique	O
key	O
,	O
the	O
"	O
content	O
address	O
"	O
.	O
</s>
<s>
The	O
file	B-Application
system	I-Application
's	O
directory	B-Application
stores	O
these	O
addresses	O
and	O
a	O
pointer	O
to	O
the	O
physical	O
storage	O
of	O
the	O
content	O
.	O
</s>
<s>
Ever-increasing	O
performance	O
of	O
traditional	O
file	B-Application
systems	I-Application
and	O
new	O
software	O
systems	O
have	O
eroded	O
the	O
value	O
of	O
legacy	O
CAS	O
systems	O
,	O
which	O
have	O
become	O
increasingly	O
rare	O
after	O
roughly	O
2018	O
.	O
</s>
<s>
However	O
,	O
the	O
principles	O
of	O
content	O
addressability	O
continue	O
to	O
be	O
of	O
great	O
interest	O
to	O
computer	O
scientists	O
,	O
and	O
form	O
the	O
core	O
of	O
numerous	O
emerging	O
technologies	O
,	O
such	O
as	O
peer-to-peer	O
file	O
sharing	O
,	O
cryptocurrencies	O
,	O
and	O
distributed	B-Architecture
computing	I-Architecture
.	O
</s>
<s>
Traditional	O
file	B-Application
systems	I-Application
generally	O
track	O
files	O
based	O
on	O
their	O
filename	B-Device
.	O
</s>
<s>
On	O
random-access	O
media	O
like	O
a	O
floppy	B-Device
disk	I-Device
,	O
this	O
is	O
accomplished	O
using	O
a	O
directory	B-Application
that	O
consists	O
of	O
some	O
sort	O
of	O
list	O
of	O
filenames	B-Device
and	O
pointers	O
to	O
the	O
data	O
.	O
</s>
<s>
The	O
pointers	O
refer	O
to	O
a	O
physical	O
location	O
on	O
the	O
disk	O
,	O
normally	O
using	O
disk	B-Application
sectors	I-Application
.	O
</s>
<s>
On	O
more	O
modern	O
systems	O
and	O
larger	O
formats	O
like	O
hard	B-Device
drives	I-Device
,	O
the	O
directory	B-Application
is	O
itself	O
split	O
into	O
many	O
subdirectories	B-Application
,	O
each	O
tracking	O
a	O
subset	O
of	O
the	O
overall	O
collection	O
of	O
files	O
.	O
</s>
<s>
Subdirectories	B-Application
are	O
themselves	O
represented	O
as	O
files	O
in	O
a	O
parent	B-Application
directory	I-Application
,	O
producing	O
a	O
hierarchy	O
or	O
tree-like	O
organization	O
.	O
</s>
<s>
The	O
series	O
of	O
directories	B-Application
leading	O
to	O
a	O
particular	O
file	O
is	O
known	O
as	O
a	O
"	O
path	O
"	O
.	O
</s>
<s>
In	O
the	O
context	O
of	O
CAS	O
,	O
these	O
traditional	O
approaches	O
are	O
referred	O
to	O
as	O
"	O
location-addressed	O
"	O
,	O
as	O
each	O
file	O
is	O
represented	O
by	O
a	O
list	O
of	O
one	O
or	O
more	O
locations	O
,	O
the	O
path	O
and	O
filename	B-Device
,	O
on	O
the	O
physical	O
storage	O
.	O
</s>
<s>
The	O
same	O
is	O
true	O
if	O
the	O
same	O
file	O
,	O
even	O
with	O
the	O
same	O
name	O
,	O
is	O
stored	O
in	O
more	O
than	O
one	O
location	O
in	O
the	O
directory	B-Application
hierarchy	O
.	O
</s>
<s>
As	O
the	O
concept	O
of	O
the	O
hierarchical	O
directory	B-Application
became	O
more	O
common	O
in	O
operating	B-General_Concept
systems	I-General_Concept
especially	O
during	O
the	O
late	O
1980s	O
,	O
this	O
sort	O
of	O
access	O
pattern	O
began	O
to	O
be	O
used	O
by	O
entirely	O
unrelated	O
systems	O
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
World	O
Wide	O
Web	O
uses	O
a	O
similar	O
pathname/filename	O
-like	O
system	O
known	O
as	O
the	O
URL	O
to	O
point	O
to	O
documents	O
.	O
</s>
<s>
The	O
same	O
document	O
on	O
another	O
web	B-Application
server	I-Application
has	O
a	O
different	O
URL	O
in	O
spite	O
of	O
being	O
identical	O
content	O
.	O
</s>
<s>
Likewise	O
,	O
if	O
an	O
existing	O
location	O
changes	O
in	O
any	O
way	O
,	O
if	O
the	O
filename	B-Device
changes	O
or	O
the	O
server	O
moves	O
to	O
a	O
new	O
domain	B-Protocol
name	I-Protocol
service	I-Protocol
name	O
,	O
the	O
document	O
is	O
no	O
longer	O
accessible	O
.	O
</s>
<s>
For	O
instance	O
,	O
the	O
ISBN	B-Library
system	O
is	O
used	O
to	O
generate	O
a	O
unique	O
number	O
for	O
every	O
book	O
.	O
</s>
<s>
If	O
one	O
performs	O
a	O
web	B-Application
search	I-Application
for	O
"	O
ISBN	B-Library
0465048994	O
"	O
,	O
one	O
will	O
be	O
provided	O
with	O
a	O
list	O
of	O
locations	O
for	O
the	O
book	O
Why	O
Information	O
Grows	O
on	O
the	O
topic	O
of	O
information	O
storage	O
.	O
</s>
<s>
CAS	O
systems	O
attempt	O
to	O
produce	O
ISBN	B-Library
like	O
results	O
automatically	O
and	O
on	O
any	O
document	O
.	O
</s>
<s>
They	O
do	O
this	O
by	O
using	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
on	O
the	O
data	O
of	O
the	O
document	O
to	O
produce	O
what	O
is	O
sometimes	O
known	O
as	O
a	O
"	O
key	O
"	O
or	O
"	O
fingerprint	O
"	O
.	O
</s>
<s>
In	O
a	O
CAS	O
system	O
,	O
the	O
directory	B-Application
does	O
not	O
map	O
filenames	B-Device
onto	O
locations	O
,	O
but	O
uses	O
the	O
keys	O
instead	O
.	O
</s>
<s>
For	O
one	O
,	O
when	O
a	O
file	O
is	O
sent	O
to	O
the	O
CAS	O
for	O
storage	O
,	O
the	O
hash	B-Error_Name
function	I-Error_Name
will	O
produce	O
a	O
key	O
and	O
then	O
check	O
to	O
see	O
if	O
that	O
key	O
already	O
exists	O
in	O
the	O
directory	B-Application
.	O
</s>
<s>
Because	O
the	O
keys	O
are	O
not	O
human-readable	O
,	O
CAS	O
systems	O
implement	O
a	O
second	O
type	O
of	O
directory	B-Application
that	O
stores	O
metadata	O
that	O
will	O
help	O
users	O
find	O
a	O
document	O
.	O
</s>
<s>
These	O
almost	O
always	O
include	O
a	O
filename	B-Device
,	O
allowing	O
the	O
classic	O
name-based	O
retrieval	B-Library
to	O
be	O
used	O
.	O
</s>
<s>
But	O
the	O
directory	B-Application
will	O
also	O
include	O
fields	O
for	O
common	O
identification	O
systems	O
like	O
ISBN	B-Library
or	O
ISSN	O
codes	O
,	O
user-provided	O
keywords	O
,	O
time	O
and	O
date	O
stamps	O
,	O
and	O
full-text	B-Application
search	I-Application
indexes	O
.	O
</s>
<s>
Users	O
can	O
search	O
these	O
directories	B-Application
and	O
retrieve	O
a	O
key	O
,	O
which	O
can	O
then	O
be	O
used	O
to	O
retrieve	O
the	O
actual	O
document	O
.	O
</s>
<s>
Using	O
a	O
CAS	O
is	O
very	O
similar	O
to	O
using	O
a	O
web	B-Application
search	I-Application
engine	I-Application
.	O
</s>
<s>
The	O
primary	O
difference	O
is	O
that	O
a	O
web	B-Application
search	I-Application
is	O
generally	O
performed	O
on	O
a	O
topic	O
basis	O
using	O
an	O
internal	O
algorithm	O
that	O
finds	O
"	O
related	O
"	O
content	O
and	O
then	O
produces	O
a	O
list	O
of	O
locations	O
.	O
</s>
<s>
If	O
,	O
for	O
instance	O
,	O
a	O
library	O
's	O
card	B-Library
catalog	I-Library
stated	O
a	O
book	O
could	O
be	O
found	O
on	O
"	O
shelf	O
43	O
,	O
bin	O
10	O
"	O
,	O
if	O
the	O
library	O
is	O
re-arranged	O
the	O
entire	O
catalog	O
has	O
to	O
be	O
updated	O
.	O
</s>
<s>
In	O
contrast	O
,	O
the	O
ISBN	B-Library
number	I-Library
will	O
not	O
change	O
and	O
the	O
book	O
can	O
be	O
found	O
by	O
looking	O
for	O
the	O
shelf	O
with	O
those	O
numbers	O
.	O
</s>
<s>
In	O
the	O
computer	O
setting	O
,	O
a	O
file	O
in	O
the	O
DOS	B-Device
filesystem	B-Application
at	O
the	O
path	O
A:\myfiles\textfile.txt	O
points	O
to	O
the	O
physical	O
storage	O
of	O
the	O
file	O
in	O
the	O
myfiles	O
subdirectory	B-Application
.	O
</s>
<s>
This	O
file	O
disappears	O
if	O
the	O
floppy	B-Device
is	O
moved	O
to	O
the	O
B	O
:	O
drive	O
,	O
and	O
even	O
moving	O
its	O
location	O
within	O
the	O
disk	O
hierarchy	O
requires	O
the	O
user-facing	O
directories	B-Application
to	O
be	O
updated	O
.	O
</s>
<s>
This	O
allows	O
files	O
to	O
be	O
moved	O
among	O
storage	O
devices	O
,	O
and	O
even	O
across	O
media	O
,	O
without	O
requiring	O
any	O
changes	O
to	O
the	O
retrieval	B-Library
.	O
</s>
<s>
Additionally	O
,	O
the	O
user-facing	O
directories	B-Application
would	O
have	O
to	O
be	O
continually	O
updated	O
with	O
these	O
"	O
new	O
"	O
files	O
,	O
which	O
would	O
become	O
polluted	O
by	O
many	O
similar	O
documents	O
that	O
would	O
make	O
searching	O
more	O
difficult	O
.	O
</s>
<s>
The	O
simplest	O
way	O
to	O
implement	O
a	O
CAS	O
system	O
is	O
to	O
have	O
all	O
of	O
the	O
files	O
stored	O
within	O
a	O
typical	O
database	O
to	O
which	O
clients	O
connect	O
to	O
add	O
,	O
query	B-Library
and	O
retrieve	O
files	O
.	O
</s>
<s>
In	O
a	O
distributed	B-Architecture
system	I-Architecture
,	O
content	O
hashes	B-Error_Name
are	O
often	O
used	O
for	O
quick	O
network-wide	O
searches	O
for	O
specific	O
files	O
,	O
or	O
to	O
quickly	O
see	O
which	O
data	O
in	O
a	O
given	O
file	O
has	O
been	O
changed	O
and	O
must	O
be	O
propagated	O
to	O
other	O
members	O
of	O
the	O
network	O
with	O
minimal	O
bandwidth	O
usage	O
.	O
</s>
<s>
A	O
hardware	O
device	O
called	O
the	O
Content	B-Device
Addressable	I-Device
File	I-Device
Store	I-Device
(	O
CAFS	O
)	O
was	O
developed	O
by	O
International	O
Computers	O
Limited	O
(	O
ICL	O
)	O
in	O
the	O
late	O
1960s	O
and	O
put	O
into	O
use	O
by	O
British	O
Telecom	O
in	O
the	O
early	O
1970s	O
for	O
telephone	O
directory	B-Application
lookups	O
.	O
</s>
<s>
The	O
user-accessible	O
search	O
functionality	O
was	O
maintained	O
by	O
the	O
disk	B-General_Concept
controller	I-General_Concept
with	O
a	O
high-level	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
so	O
users	O
could	O
send	O
queries	B-Library
into	O
what	O
appeared	O
to	O
be	O
a	O
black	B-Device
box	I-Device
that	O
returned	O
documents	O
.	O
</s>
<s>
In	O
addition	O
to	O
CAS	O
,	O
a	O
number	O
of	O
similar	O
products	O
emerged	O
that	O
added	O
CAS-like	O
capabilities	O
to	O
existing	O
products	O
;	O
notable	O
among	O
these	O
was	O
IBM	B-General_Concept
Tivoli	I-General_Concept
Storage	I-General_Concept
Manager	I-General_Concept
.	O
</s>
<s>
The	O
rise	O
of	O
cloud	B-Architecture
computing	I-Architecture
and	O
the	O
associated	O
elastic	B-General_Concept
cloud	I-General_Concept
storage	I-General_Concept
systems	O
like	O
Amazon	B-General_Concept
S3	I-General_Concept
further	O
diluted	O
the	O
value	O
of	O
dedicated	O
CAS	O
systems	O
.	O
</s>
<s>
CAS	O
was	O
not	O
originally	O
associated	O
with	O
peer-to-peer	O
applications	O
until	O
the	O
2000s	O
,	O
when	O
rapidly	O
proliferating	O
Internet	O
access	O
in	O
homes	O
and	O
businesses	O
led	O
to	O
a	O
large	O
amount	O
of	O
computer	O
users	O
who	O
wanted	O
to	O
swap	O
files	O
,	O
originally	O
doing	O
so	O
on	O
centrally	O
managed	O
services	O
like	O
Napster	B-Application
.	O
</s>
<s>
However	O
,	O
an	O
injunction	O
against	O
Napster	B-Application
prompted	O
the	O
independent	O
development	O
of	O
file-sharing	O
services	O
such	O
as	O
BitTorrent	B-Protocol
,	O
which	O
could	O
not	O
be	O
centrally	O
shut	O
down	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
the	O
growth	O
of	O
the	O
open-source	B-Application
software	I-Application
movement	O
in	O
the	O
2000s	O
led	O
to	O
the	O
rapid	O
proliferation	O
of	O
CAS-based	O
services	O
such	O
as	O
Git	B-Application
,	O
a	O
version	B-Architecture
control	I-Architecture
system	I-Architecture
that	O
uses	O
numerous	O
cryptographic	O
functions	O
such	O
as	O
Merkle	B-Algorithm
trees	I-Algorithm
to	O
enforce	O
data	O
integrity	O
between	O
users	O
and	O
allow	O
for	O
multiple	O
versions	O
of	O
files	O
with	O
minimal	O
disk	O
and	O
network	O
usage	O
.	O
</s>
<s>
Around	O
this	O
time	O
,	O
individual	O
users	O
of	O
public-key	B-Application
cryptography	I-Application
used	O
CAS	O
to	O
store	O
their	O
public	B-Application
keys	I-Application
on	O
systems	O
such	O
as	O
key	O
servers	O
.	O
</s>
<s>
The	O
rise	O
of	O
mobile	O
computing	O
and	O
high	O
capacity	O
mobile	O
broadband	O
networks	O
in	O
the	O
2010s	O
,	O
coupled	O
with	O
increasing	O
reliance	O
on	O
web	B-Application
applications	I-Application
for	O
everyday	O
computing	O
tasks	O
,	O
strained	O
the	O
existing	O
location-addressed	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
model	I-Operating_System
commonplace	O
among	O
Internet	O
services	O
,	O
leading	O
to	O
an	O
accelerated	O
pace	O
of	O
link	O
rot	O
and	O
an	O
increased	O
reliance	O
on	O
centralized	O
cloud	B-Architecture
hosting	I-Architecture
.	O
</s>
<s>
Furthermore	O
,	O
growing	O
concerns	O
about	O
the	O
centralization	O
of	O
computing	O
power	O
in	O
the	O
hands	O
of	O
large	O
technology	O
companies	O
,	O
potential	O
monopoly	B-Application
power	O
abuses	O
,	O
and	O
privacy	O
concerns	O
led	O
to	O
a	O
number	O
of	O
projects	O
created	O
with	O
the	O
goal	O
of	O
creating	O
more	O
decentralized	O
systems	O
.	O
</s>
<s>
Bitcoin	B-Protocol
uses	O
CAS	O
and	O
public/private	B-Application
key	I-Application
pairs	I-Application
to	O
manage	O
wallet	O
addresses	O
,	O
as	O
do	O
most	O
other	O
cryptocurrencies	O
.	O
</s>
<s>
IPFS	B-Protocol
uses	O
CAS	O
to	O
identify	O
and	O
address	O
communally	O
hosted	O
files	O
on	O
its	O
network	O
.	O
</s>
<s>
Numerous	O
other	O
peer-to-peer	O
systems	O
designed	O
to	O
run	O
on	O
smartphones	B-Application
,	O
which	O
often	O
access	O
the	O
Internet	O
from	O
varying	O
locations	O
,	O
utilize	O
CAS	O
to	O
store	O
and	O
access	O
user	O
data	O
for	O
both	O
convenience	O
and	O
data	O
privacy	O
purposes	O
,	O
such	O
as	O
secure	O
instant	B-Application
messaging	I-Application
.	O
</s>
<s>
The	O
Centera	O
CAS	O
system	O
consists	O
of	O
a	O
series	O
of	O
networked	O
nodes	O
(	O
typically	O
large	O
servers	O
running	O
Linux	B-Application
)	O
,	O
divided	O
between	O
storage	O
nodes	O
and	O
access	O
nodes	O
.	O
</s>
<s>
The	O
access	O
nodes	O
maintain	O
a	O
synchronized	O
directory	B-Application
of	O
content	O
addresses	O
,	O
and	O
the	O
corresponding	O
storage	O
node	O
where	O
each	O
address	O
can	O
be	O
found	O
.	O
</s>
<s>
When	O
a	O
new	O
data	O
element	O
,	O
or	O
blob	B-General_Concept
,	O
is	O
added	O
,	O
the	O
device	O
calculates	O
a	O
hash	B-Error_Name
of	O
the	O
content	O
and	O
returns	O
this	O
hash	B-Error_Name
as	O
the	O
blob	B-General_Concept
's	O
content	O
address	O
.	O
</s>
<s>
As	O
mentioned	O
above	O
,	O
the	O
hash	B-Error_Name
is	O
searched	O
to	O
verify	O
that	O
identical	O
content	O
is	O
not	O
already	O
present	O
.	O
</s>
<s>
When	O
a	O
content	O
address	O
is	O
provided	O
to	O
the	O
device	O
,	O
it	O
first	O
queries	B-Library
the	O
directory	B-Application
for	O
the	O
physical	O
location	O
of	O
the	O
specified	O
content	O
address	O
.	O
</s>
<s>
The	O
information	O
is	O
then	O
retrieved	O
from	O
a	O
storage	O
node	O
,	O
and	O
the	O
actual	O
hash	B-Error_Name
of	O
the	O
data	O
recomputed	O
and	O
verified	O
.	O
</s>
<s>
Within	O
the	O
Centera	O
system	O
,	O
each	O
content	O
address	O
actually	O
represents	O
a	O
number	O
of	O
distinct	O
data	O
blobs	B-General_Concept
,	O
as	O
well	O
as	O
optional	O
metadata	O
.	O
</s>
<s>
Whenever	O
a	O
client	O
adds	O
an	O
additional	O
blob	B-General_Concept
to	O
an	O
existing	O
content	O
block	O
,	O
the	O
system	O
recomputes	O
the	O
content	O
address	O
.	O
</s>
<s>
To	O
provide	O
additional	O
data	O
security	O
,	O
the	O
Centera	O
access	O
nodes	O
,	O
when	O
no	O
read	O
or	O
write	O
operation	O
is	O
in	O
progress	O
,	O
constantly	O
communicate	O
with	O
the	O
storage	O
nodes	O
,	O
checking	O
the	O
presence	O
of	O
at	O
least	O
two	O
copies	O
of	O
each	O
blob	B-General_Concept
as	O
well	O
as	O
their	O
integrity	O
.	O
</s>
<s>
IBM	O
has	O
another	O
flavor	O
of	O
CAS	O
which	O
can	O
be	O
software-based	O
,	O
Tivoli	B-General_Concept
Storage	I-General_Concept
manager	I-General_Concept
5.3	O
,	O
or	O
hardware-based	O
,	O
the	O
IBM	O
DR550	O
.	O
</s>
<s>
The	O
architecture	O
is	O
different	O
in	O
that	O
it	O
is	O
based	O
on	O
hierarchical	B-Application
storage	I-Application
management	I-Application
(	O
HSM	O
)	O
design	O
which	O
provides	O
some	O
additional	O
flexibility	O
such	O
as	O
being	O
able	O
to	O
support	O
not	O
only	O
WORM	B-Device
disk	O
but	O
WORM	B-Device
tape	O
and	O
the	O
migration	O
of	O
data	O
from	O
WORM	B-Device
disk	O
to	O
WORM	B-Device
tape	O
and	O
vice	O
versa	O
.	O
</s>
<s>
Each	O
container	O
is	O
addressed	O
by	O
its	O
hash	B-Error_Name
value	I-Error_Name
.	O
</s>
<s>
The	O
container	O
is	O
not	O
changeable	O
,	O
and	O
the	O
hash	B-Error_Name
value	I-Error_Name
is	O
fixed	O
after	O
the	O
write	O
process	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
content-addressed	O
storage	O
servers	O
,	O
Venti	B-Application
,	O
was	O
originally	O
developed	O
for	O
Plan	B-Operating_System
9	I-Operating_System
from	I-Operating_System
Bell	I-Operating_System
Labs	I-Operating_System
and	O
is	O
now	O
also	O
available	O
for	O
Unix-like	O
systems	O
as	O
part	O
of	O
Plan	B-Application
9	I-Application
from	I-Application
User	I-Application
Space	I-Application
.	O
</s>
<s>
The	O
first	O
step	O
towards	O
an	O
open-source	B-Application
CAS+	O
implementation	O
is	O
Twisted	O
Storage	O
.	O
</s>
<s>
Tahoe	B-General_Concept
Least-Authority	I-General_Concept
File	I-General_Concept
Store	I-General_Concept
is	O
an	O
open	O
source	O
implementation	O
of	O
CAS	O
.	O
</s>
<s>
Git	B-Application
is	O
a	O
userspace	B-Operating_System
CAS	O
filesystem	B-Application
.	O
</s>
<s>
Git	B-Application
is	O
primarily	O
used	O
as	O
a	O
source	O
code	O
control	O
system	O
.	O
</s>
<s>
git-annex	B-Protocol
is	O
a	O
distributed	O
file	O
synchronization	O
system	O
that	O
uses	O
content-addressable	B-Data_Structure
storage	I-Data_Structure
for	O
files	O
it	O
manages	O
.	O
</s>
<s>
It	O
relies	O
on	O
Git	B-Application
and	O
symbolic	B-Application
links	I-Application
to	O
index	O
their	O
filesystem	B-Application
location	O
.	O
</s>
<s>
Project	B-Device
Honeycomb	I-Device
is	O
an	O
open-source	B-Application
API	B-Application
for	O
CAS	O
systems	O
.	O
</s>
<s>
The	O
XAM	B-General_Concept
interface	O
was	O
developed	O
under	O
the	O
auspices	O
of	O
the	O
Storage	O
Networking	O
Industry	O
Association	O
.	O
</s>
<s>
Perkeep	B-Language
is	O
a	O
recent	O
project	O
to	O
bring	O
the	O
advantages	O
of	O
content-addressable	B-Data_Structure
storage	I-Data_Structure
"	O
to	O
the	O
masses	O
"	O
.	O
</s>
<s>
It	O
is	O
intended	O
to	O
be	O
used	O
for	O
a	O
wide	O
variety	O
of	O
use	O
cases	O
,	O
including	O
distributed	O
backup	O
,	O
a	O
snapshotted-by-default	O
,	O
a	O
version-controlled	O
filesystem	B-Application
,	O
and	O
decentralized	O
,	O
permission-controlled	O
filesharing	O
.	O
</s>
<s>
Irmin	O
is	O
an	O
OCaml	B-Language
"	O
library	O
for	O
persistent	O
stores	O
with	O
built-in	O
snapshot	O
,	O
branching	O
and	O
reverting	O
mechanisms	O
"	O
;	O
the	O
same	O
design	O
principles	O
as	O
Git	B-Application
.	O
</s>
<s>
Cassette	O
is	O
an	O
open-source	B-Application
CAS	O
implementation	O
for	O
C#	O
/.NET	O
.	O
</s>
<s>
Keep	O
is	O
an	O
open-source	B-Application
content-addressable	O
distributed	O
storage	O
system	O
.	O
</s>
<s>
Infinit	O
is	O
a	O
content-addressable	O
and	O
decentralized	O
(	O
peer-to-peer	O
)	O
storage	O
platform	O
that	O
was	O
acquired	O
by	O
Docker	B-Language
Inc	O
.	O
</s>
<s>
InterPlanetary	B-Protocol
File	I-Protocol
System	I-Protocol
(	O
IPFS	B-Protocol
)	O
,	O
is	O
a	O
content-addressable	O
,	O
peer-to-peer	O
hypermedia	O
distribution	O
protocol	O
.	O
</s>
<s>
casync	B-Application
is	O
a	O
Linux	B-Application
software	O
utility	O
by	O
Lennart	O
Poettering	O
to	O
distribute	O
frequently-updated	O
file	B-Application
system	I-Application
images	O
over	O
the	O
Internet	O
.	O
</s>
