<s>
CacheFS	B-General_Concept
is	O
the	O
name	O
used	O
for	O
several	O
similar	O
software	O
technologies	O
designed	O
to	O
speed	O
up	O
distributed	B-Protocol
file	I-Protocol
system	I-Protocol
file	B-Application
access	I-Application
for	O
networked	O
computers	O
.	O
</s>
<s>
These	O
technologies	O
operate	O
by	O
storing	O
(	O
cached	B-Protocol
)	O
copies	O
of	O
files	O
on	O
secondary	O
memory	O
,	O
typically	O
a	O
local	O
hard	B-Device
disk	I-Device
,	O
so	O
that	O
if	O
a	O
file	O
is	O
accessed	O
again	O
,	O
it	O
can	O
be	O
done	O
locally	O
at	O
much	O
higher	O
speeds	O
than	O
networks	O
typically	O
allow	O
.	O
</s>
<s>
CacheFS	B-General_Concept
software	O
is	O
used	O
on	O
several	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Another	O
version	O
was	O
written	O
for	O
Linux	B-Application
and	O
released	O
in	O
2003	O
.	O
</s>
<s>
Network	B-Architecture
filesystems	B-Application
are	O
dependent	O
on	O
a	O
network	B-Architecture
link	O
and	O
a	O
remote	O
server	B-Application
;	O
obtaining	O
a	O
file	O
from	O
such	O
a	O
filesystem	B-Application
can	O
be	O
significantly	O
slower	O
than	O
getting	O
the	O
file	O
locally	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
it	O
can	O
be	O
desirable	O
to	O
cache	O
data	O
from	O
these	O
filesystems	B-Application
on	O
a	O
local	O
disk	O
,	O
thus	O
potentially	O
speeding	O
up	O
future	O
accesses	O
to	O
that	O
data	O
by	O
avoiding	O
the	O
need	O
to	O
go	O
to	O
the	O
network	B-Architecture
and	O
fetch	O
it	O
again	O
.	O
</s>
<s>
The	O
software	O
has	O
to	O
check	O
that	O
the	O
remote	O
file	O
has	O
not	O
changed	O
since	O
it	O
was	O
cached	B-Protocol
,	O
but	O
this	O
is	O
much	O
faster	O
than	O
reading	O
the	O
whole	O
file	O
again	O
.	O
</s>
<s>
Sprite	B-Operating_System
used	O
large	O
disk	O
block	O
caches	O
.	O
</s>
<s>
These	O
were	O
located	O
in	O
main-memory	O
to	O
achieve	O
high	O
performance	O
in	O
its	O
file	B-Application
system	I-Application
.	O
</s>
<s>
The	O
term	O
CacheFS	B-General_Concept
has	O
found	O
little	O
or	O
no	O
use	O
to	O
describe	O
caches	O
in	O
main	O
memory	O
.	O
</s>
<s>
The	O
first	O
CacheFS	B-General_Concept
implementation	O
,	O
in	O
6502	O
assembler	O
,	O
was	O
a	O
write	O
through	O
cache	O
developed	O
by	O
Mathew	O
R	O
Mathews	O
at	O
Grossmont	O
College	O
.	O
</s>
<s>
It	O
was	O
used	O
from	O
fall	O
1986	O
to	O
spring	O
1990	O
on	O
three	O
diskless	O
64kB	O
main	O
memory	O
Apple	O
IIe	O
computers	O
to	O
cache	O
files	O
from	O
a	O
Nestar	O
file	O
server	B-Application
onto	O
Big	O
Board	O
,	O
a	O
1MB	O
DRAM	O
secondary	O
memory	O
device	O
partitioned	O
into	O
CacheFS	B-General_Concept
and	O
TmpFS	O
.	O
</s>
<s>
Pineapple	O
DOS	O
features	O
,	O
including	O
caching	O
,	O
were	O
unnamed	O
;	O
the	O
name	O
CacheFS	B-General_Concept
was	O
introduced	O
seven	O
years	O
later	O
by	O
Sun	O
Microsystems	O
.	O
</s>
<s>
The	O
first	O
Unix	O
CacheFS	B-General_Concept
implementation	O
was	O
developed	O
by	O
Sun	O
Microsystems	O
and	O
released	O
in	O
the	O
Solaris	B-Application
2.3	I-Application
operating	O
system	O
release	O
in	O
1993	O
,	O
as	O
part	O
of	O
an	O
expanded	O
feature	O
set	O
for	O
the	O
NFS	B-Protocol
or	O
Network	B-Protocol
File	I-Protocol
System	I-Protocol
suite	O
known	O
as	O
Open	B-Protocol
Network	I-Protocol
Computing	I-Protocol
Plus	O
(	O
ONC+	O
)	O
.	O
</s>
<s>
It	O
was	O
subsequently	O
used	O
in	O
other	O
UNIX	O
operating	O
systems	O
such	O
as	O
IRIX	B-Operating_System
(	O
starting	O
with	O
the	O
5.3	O
release	O
in	O
1994	O
)	O
.	O
</s>
<s>
Linux	B-Application
operating	I-Application
systems	I-Application
now	O
commonly	O
use	O
a	O
new	O
version	O
of	O
CacheFS	B-General_Concept
developed	O
by	O
David	O
Howells	O
.	O
</s>
<s>
Howells	O
appears	O
to	O
have	O
rewritten	O
CacheFS	B-General_Concept
from	O
scratch	O
,	O
not	O
using	O
Sun	O
's	O
original	O
code	O
.	O
</s>
<s>
The	O
Linux	B-Application
CacheFS	B-General_Concept
currently	O
is	O
designed	O
to	O
operate	O
on	O
Andrew	B-Application
File	I-Application
System	I-Application
and	O
Network	B-Protocol
File	I-Protocol
System	I-Protocol
(	O
NFS	B-Protocol
)	O
filesystems	B-Application
.	O
</s>
<s>
Because	O
of	O
its	O
similar	O
naming	O
to	O
FS-Cache	O
,	O
CacheFS	B-General_Concept
 '	O
terminology	B-Language
is	O
confusing	O
to	O
outsiders	O
.	O
</s>
<s>
CacheFS	B-General_Concept
is	O
a	O
backend	O
for	O
FS-Cache	O
and	O
handles	O
the	O
actual	O
data	O
storage	O
and	O
retrieval	O
.	O
</s>
<s>
FS-Cache	O
passes	O
the	O
requests	O
from	O
netfs	O
to	O
CacheFS	B-General_Concept
.	O
</s>
<s>
The	O
cache	O
facility/layer	O
between	O
the	O
cache	O
backends	O
just	O
like	O
CacheFS	B-General_Concept
and	O
NFS	B-Protocol
or	O
AFS	O
.	O
</s>
<s>
CacheFS	B-General_Concept
is	O
a	O
Filesystem	B-Application
for	O
the	O
FS-Cache	O
facility	O
.	O
</s>
<s>
A	O
block	O
device	O
can	O
be	O
used	O
as	O
cache	O
by	O
simply	O
mounting	B-Application
it	O
.	O
</s>
<s>
Daemon	B-Operating_System
using	O
an	O
existing	O
filesystem	B-Application
(	O
ext3	B-Application
with	O
)	O
as	O
cache	O
.	O
</s>
<s>
Applications	O
should	O
just	O
be	O
able	O
to	O
use	O
NFS	B-Protocol
files	O
as	O
normal	O
,	O
without	O
any	O
knowledge	O
of	O
there	O
being	O
a	O
cache	O
.	O
</s>
